Method and device for controlling currents of synchronous motor

ABSTRACT

There are performed converting electric currents Iu, Iv, and Iw flowing through the synchronous motor into a d-axis actual current Idfb and a q-axis actual current Iqfb on rotational coordinate axes which rotate synchronously with a rotor magnetic flux vector, on the basis of an actual position θ of the rotor of the synchronous motor; estimating a d-axis simulated current Idob and a q-axis simulated current Iqob on the basis of the d-axis actual current Idfb, the q-axis actual current Iqfb, a d-axis actual voltage command Vdref, and a q-axis actual voltage command Vqref; generating a d-axis actual voltage command Vdref and a q-axis actual voltage command Vqref on the basis of a d-axis current command Idref, a q-axis current command Iqref, a d-axis simulated current Idob, and a q-axis simulated current Iqob; and converting the d-axis actual voltage command Vdref and the q-axis actual voltage command Vqref into actual voltage commands Vuref, Vvref, and Vwref on the basis of the actual position θ of a rotor of the synchronous motor. As a result, there can be provided a method and apparatus for controlling an electric current of a synchronous motor, which can provide a superior current response characteristic regardless of the influence of temperature.

FIELD OF THE INVENTION

The invention relates to a method and apparatus for controlling anelectric current of a linear motor and a synchronous motor for driving aload machine; e.g., a table or a robot arm of a machine tool.

RELATED ART

A current controller (hereinafter also called a “first related-artdevice”) of a synchronous motor such as shown in FIG. 7 has hithertobeen available as a current controller of a related-art synchronousmotor for achieving a high-speed response characteristic.

A first related-art device shown in FIG. 7 is described as a currentcontroller of a synchronous motor utilizing a current feedforward inJP-A-11-18469. The first related-art device will now be describedbriefly by reference to FIG. 7.

In FIG. 7, reference numeral 1 designates a synchronous motor; 2designates an actual position observation device; 3 designates an actualcurrent observation section; 4 designates a power conversion circuit; 5designates a first coordinate converter; 6 designates a secondcoordinate converter; 20 designates a feedback control section; 12designates a feedforward control section; and 13 designates a voltagecommand synthesis section.

The actual current observation section 3 observes an electric current oftwo phases or more of the synchronous motor 1, thereby providing actualcurrents Iu, Iv, and Iw.

The actual position observation device 2 functions as an encoder andprovides an actual position θ of a rotor of the synchronous motor 1.

On the basis of the actual position θ and the actual currents Iu, Iv,and Iw, the second coordinate converter 6 converts the currents into ad-axis actual current Idfb and a q-axis actual current Iqfb, which fallon a rotational coordinate axis that rotates in synchronism with a rotormagnetic flux vector of the synchronous motor.

The first coordinate converter 5 converts a d-axis actual voltagecommand Vdref and a q-axis actual voltage command Vqref into actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ so as to be supplied to the power conversion circuit 4.

On the basis of the d-axis current command Idref and the q-axis currentcommand Iqref, the feedforward control section 12 produces a d-axissecond simulated current command Idff, a q-axis second simulated currentcommand Iqff, a d-axis second simulated voltage command Vdff, and aq-axis second simulated voltage command Vqff.

On the basis of the d-axis second simulated current command Idff, theq-axis second simulated current command Iqff, the d-axis simulatedcurrent, and the q-axis simulated current, the feedback control section20 produces ad-axis third simulated voltage command vdfb and a q-axisthird simulated voltage command Vqfb.

On the basis of the d-axis second simulated voltage command Vdff, theq-axis second simulated voltage command Vqff, the d-axis third simulatedvoltage command Vdfb, and the q-axis third simulated voltage commandVqfb, the voltage command synthesizer 13 produces a d-axis actualvoltage command Vdref and a q-axis actual voltage command Vqref.

In the current controller of the above-described synchronous motor, thefeedforward control section 12 produces the d-axis second simulatedcurrent command Idff, the q-axis second simulated current Iqff, thed-axis second simulated voltage command vdff, and the q-axis secondsimulated voltage command Vqff on the basis of the d-axis currentcommand Idref and the q-axis current command Iqref. These producedcurrent commands are provided to the feedback control section 20 as wellas to the voltage command synthesizer 13, whereby current control withhigh-speed response can be attained without generating an overshoot ofstep response.

A controller of a synchronous motor (hereinafter called a “secondrelated-art device”) such as that shown in FIG. 10 has already beenavailable as another controller of the related-art synchronous motor.

The second related-art device will now be described briefly by referenceto FIG. 10.

In FIG. 10, reference numeral 81 designates a synchronous motor; 82designates an actual position observation device; 83 designates anactual current observation section; 84 designates a power conversioncircuit; 85 designates a second coordinate conversion circuit; 86designates a first coordinate conversion circuit; 87 designates acurrent control section; 88 designates a machine control section; and 91designates a differentiator.

The actual current observation section 83 observes an electric currentof two phases or more of the synchronous motor 81, thereby supplying theactual currents Iu, Iv, and Iw.

The actual position observation device 82 functions as an encoder andprovides an actual rotor position θ of the synchronous motor 81.

On the basis of the actual position θ as well as the actual currents Iu,Iv, and Iw, the first coordinate conversion circuit 86 converts thesecurrents into a d-axis actual current Id and a q-axis actual current Iq,which fall on a rotational coordinate axis that rotates in synchronismwith a rotor magnetic flux vector of the synchronous motor.

On the basis of the actual position θ, the second coordinate converter85 converts a d-axis voltage command vdref and a q-axis voltage commandVqref into actual voltage commands Vuref, Vvref, and Vwref so as to besupplied to the power conversion circuit 84.

On the basis of a torque command Tref, the d-axis actual current Id, theq-axis actual current Iq, and the actual position θ, the current controlsection 87 performs current control operation and produces the d-axisvoltage command Vdref and the q-axis voltage command Vqref.

On the basis of the actual position θ, the differentiator 91 produces anestimated speed “w”. For instance, the following method is commonlyemployed.w(k)=(θ(k)−θ(k−1))/Twhere T is a sampling time and (k) is a signal value at a time k*T.

The machine control section 88 performs machine control operation on thebasis of the actual command θref, the actual position θ of the rotor ofthe synchronous motor, and the estimated speed “w,” thereby providingthe torque command Tref.

The actual position θ and the estimated speed “w” are supplied to themachine control section 88, which enables the synchronous motor 81 torespond stably and quickly to the actual command θref.

However, the first related-art device is intended for improving aresponse characteristic with respect to the d-axis current command Idrefand the q-axis current command Iqref, and it is not intended forenhancing a feedback characteristic. Accordingly, when variations arisein parameters or power of the synchronous motor 1 or the powerconversion section 4 due to influence of temperature, vibration orovershooting might be generated in the step response, which deterioratesa response characteristic of the electric current.

DISCLOSURE OF THE INVENTION

Consequently, a first object of the invention is to provide a method andapparatus for controlling an electric current of a synchronous motor,which provides a superior current response characteristic even whenvariations arise in parameters or power of the synchronous motor 1 andthe power conversion section 4 under the influence of temperature.

In the second related-art device, the actual position θ has beenquantized, and a quantization error is present in θ(k). We havewm(k)≠w(k),where wm denotes an actual speed of a synchronous motor.

For instance, in the case of an encoder which produces 10000pulses/rotation, maximum positional accuracy of the actual position θ is1/10000 rotations.

When a sampling time is 100 μs, “w” has a resolving power of 1 pulse/100μs; that is, 10000 pulses/s or 60 rpm.

When the sampling time is 10 μs, the “w” has a resolving power of 1pulse/10 μs; that is, 100000 pulses/s or 600 rpm.

In the case of a single encoder, the resolving power of “w” becomesconsiderably deteriorated as a result of shortening of the samplingtime. Therefore, a vibration component in the torque command Trefproduced by the machine control section 88 becomes greater, and thespeed gain cannot be set to a high level, which in turn deterioratesresponsiveness of the synchronous motor.

In order to solve the problem, the resolving power of the encoder hashitherto been increased. However, an increase in resolving power of theencoder ends up increasing the cost.

Therefore, a second object of the invention is to provide a method andapparatus for controlling a synchronous motor which provides superiorresponsiveness and robustness without an increase in resolving power ofan encoder even when a sampling time is shortened.

In order to achieve the first object, an invention which is defined inclaim 1 and pertains to a method for controlling an electric current ofa synchronous motor is directed toward a method for controlling anelectric current of a synchronous motor in which a power conversioncircuit is provided with an appropriate actual voltage command such thatan electric current flowing through the synchronous motor fed with powerfrom the power conversion circuit coincides with a current command, themethod comprising: conversion of electric currents Iu, Iv, and Iwflowing through the synchronous motor into a d-axis actual current Idfband a q-axis actual current Iqfb on rotational coordinate axes whichrotate in synchronism with a rotor magnetic flux vector, on the basis ofan actual position θ of the rotor of the synchronous motor; estimationof a d-axis simulated current Idob and a q-axis simulated current Iqobon the basis of the d-axis actual current Idfb, the q-axis actualcurrent Iqfb, a d-axis actual voltage command Vdref, and a q-axis actualvoltage command Vqref; generation of the d-axis actual voltage commandVdref and the q-axis actual voltage command Vqref on the basis of ad-axis current command Idref, a q-axis current command Iqref, the d-axissimulated current Idob, and the q-axis simulated current Iqob; andconversion of the d-axis actual voltage command Vdref and the q-axisactual voltage command Vqref into actual voltage commands Vuref, Vvref,and Vwref on the basis of the actual position θ of a rotor of thesynchronous motor.

According to the method for controlling an electric current of asynchronous motor defined in claim 1, a current feedback gain can be setto a high level. A superior current response characteristic can beprovided even when variations arise in parameters or power of thesynchronous motor 1 and the power conversion section 4 under theinfluence of temperature.

A method for controlling an electric current of a synchronous motordefined in claim 2 is directed toward a method for controlling anelectric current of a synchronous motor in which a power conversioncircuit is provided with an appropriate actual voltage command such thatan electric current flowing through the synchronous motor fed with powerfrom the power conversion circuit coincides with a current command, themethod comprising: conversion of electric currents Iu, Iv, and Iwflowing through the synchronous motor into a d-axis actual current Idfband a q-axis actual current Iqfb on rotational coordinate axes whichrotate in synchronism with a rotor magnetic flux vector, on the basis ofan actual position θ of the rotor of the synchronous motor; estimationof a d-axis simulated current Idob and a q-axis simulated current Iqobon the basis of the d-axis actual current Idfb, the q-axis actualcurrent Iqfb, a d-axis first simulated voltage command Vdo, and a q-axisfirst simulated voltage command Vqo; generation of the d-axis firstsimulated voltage command Vdo and the q-axis first simulated voltagecommand Vqo on the basis of a d-axis current command Idref, a q-axiscurrent command Iqref, the d-axis simulated current Idob, and the q-axissimulated current Iqob; addition of an induced voltage to the d-axisfirst simulated voltage command Vdo and the q-axis first simulatedvoltage command Vqo on the basis of actual position θ of a rotor of thesynchronous motor, to thereby produce a d-axis actual voltage commandVdref and a q-axis actual voltage command Vqref; and conversion of thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref into actual voltage commands Vuref, Vvref, and Vwref onthe basis of the actual position θ of a rotor of the synchronous motor.

According to the method for controlling an electric current of asynchronous motor defined in claim 2, a current feedback gain can be setto a high level. Hence, even when variations arise in parameters orpower of the synchronous motor 1 and the power conversion circuit 4under the influence of temperature, a superior current responsecharacteristic can be obtained. Further, even when an abrupt change hasarisen in the rotational speed of the synchronous motor, a superiorcurrent response characteristic can be obtained.

A method for controlling an electric current of a synchronous motordefined in claim 3 is directed toward a method for controlling anelectric current of a synchronous motor in which a power conversioncircuit is provided with an appropriate actual voltage command such thatan electric current flowing through the synchronous motor fed with powerfrom the power conversion circuit coincides with a current command, themethod comprising: generation of a d-axis second simulated currentcommand Idff, a q-axis second simulated current command Iqff, a d-axissecond simulated voltage command Vdff, and a q-axis second simulatedvoltage command Vqff on the basis of a d-axis current command Idref anda q-axis current command Iqref; conversion of electric currents Iu, Iv,and Iw flowing through the synchronous motor into a d-axis actualcurrent Idfb and a q-axis actual current Iqfb on rotational coordinateaxes which rotate synchronously with a rotor magnetic flux vector, onthe basis of an actual position θ of the rotor of the synchronous motor;estimation of ad-axis simulated current Idob and a q-axis simulatedcurrent Iqob on the basis of the d-axis actual current Idfb, the q-axisactual current Iqfb, a d-axis first simulated voltage command Vdo, and aq-axis first simulated voltage command Vqo; generation of a d-axis thirdsimulated voltage command Vdfb and a q-axis third simulated voltagecommand Vqfb on the basis of the d-axis second simulated current commandIdff, the q-axis second simulated current command Iqff, the d-axissimulated current Idob, and the q-axis simulated current Iqob;generation of the d-axis first simulated voltage command Vdo and theq-axis first simulated voltage command Vqo on the basis of the d-axisthird simulated voltage command Vdfb, the q-axis third simulated voltagecommand Vqfb, the d-axis second simulated voltage command Vdff, and theq-axis second simulated voltage command Vqff; addition of an inducedvoltage to the d-axis first simulated voltage command Vdo and the q-axisfirst simulated voltage command Vqo on the basis of an actual position θof a rotor of the synchronous motor, to thereby produce a d-axis actualvoltage command Vdref and a q-axis actual voltage command Vqref; andconversion of the d-axis actual voltage command Vdref and the q-axisactual voltage command Vqref into actual voltage commands Vuref, Vvref,and Vwref on the basis of the actual position θ of a rotor of thesynchronous motor.

According to the method for controlling an electric current of asynchronous motor defined in claim 3, a current feedback gain can be setto a high level. Hence, even when variations arise in parameters orpower of the synchronous motor 1 and the power conversion circuit 4under the influence of temperature, a superior current responsecharacteristic can be obtained. Further, even when an abrupt change hasarisen in the rotational speed of the synchronous motor, a superiorcurrent response characteristic can be obtained. Moreover, a fastercurrent response characteristic in response to the command can beobtained.

A method for controlling an electric current of a synchronous motordefined in claim 4 is directed toward a method for controlling anelectric current of a synchronous motor in which a power conversioncircuit is provided with an appropriate actual voltage command such thatan electric current flowing through the synchronous motor fed with powerfrom the power conversion circuit coincides with a current command, themethod comprising: conversion of electric currents Iu, Iv, and Iwflowing through the synchronous motor into a d-axis actual current Idfband a q-axis actual current Iqfb on rotational coordinate axes whichrotate synchronously with a rotor magnetic flux vector, on the basis ofan actual position θ of the rotor of the synchronous motor; estimationof a d-axis simulated current Idob, a q-axis simulated current Iqob, ad-axis simulated disturbance voltage Vdob, and a q-axis simulatedvoltage command Vqob on the basis of the d-axis actual current Idfb, theq-axis actual current Iqfb, a d-axis actual voltage command Vdref, and aq-axis actual voltage command Vqref; generation of a d-axis firstsimulated voltage command Vdo and a q-axis first simulated voltagecommand Vqo on the basis of a d-axis current command Idref, a q-axiscurrent command Iqref, the d-axis simulated current Idob, and the q-axissimulated current Iqob; generation of the d-axis actual voltage commandVdref and the q-axis actual voltage command Vqref on the basis of thed-axis third simulated voltage command Vdfb, the q-axis third simulatedvoltage command Vqfb, the d-axis simulated disturbance voltage Vdob, andthe q-axis simulated disturbance voltage Vqob; and conversion of thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref into actual voltage commands Vuref, Vvref, and Vwref onthe basis of the actual position θ of a rotor of the synchronous motor.

According to the method for controlling an electric current of asynchronous motor defined in claim 4, a current feedback gain can be setto a high level. Hence, even when variations arise in parameters orpower of the synchronous motor 1 and the power conversion circuit 4under the influence of temperature, a superior current responsecharacteristic can be obtained. Further, even when an abrupt change orfluctuation has arisen in a parameter of the synchronous motor 1 andthat of the power conversion circuit 4, a superior current responsecharacteristic can be obtained.

A method for controlling an electric current of a synchronous motordefined in claim 5 is directed toward a method for controlling anelectric current of a synchronous motor in which a power conversioncircuit is provided with an appropriate actual voltage command such thatan electric current flowing through the synchronous motor fed with powerfrom the power conversion circuit coincides with a current command, themethod comprising: generation of a d-axis second simulated currentcommand Idff, a q-axis second simulated current command Iqff, a d-axissecond simulated voltage command Vdff, and a q-axis second simulatedvoltage command Vqff on the basis of a d-axis current command Idref anda q-axis current command Iqref; conversion of electric currents Iu, Iv,and Iw flowing through the synchronous motor into a d-axis actualcurrent Idfb and a q-axis actual current Iqfb on rotational coordinateaxes which rotate synchronously with a rotor magnetic flux vector, onthe basis of an actual position θ of the rotor of the synchronous motor;estimation of a d-axis simulated current Idob, a q-axis simulatedcurrent Iqob, a q-axis simulated disturbance voltage Vdob, and a q-axissimulated disturbance voltage Vqob on the basis of the d-axis actualcurrent Idfb, the q-axis actual current Iqfb, ad-axis actual voltagecommand Vdref, and a q-axis actual voltage command Vqref; generation ofa d-axis third simulated voltage command Vdfb and a q-axis thirdsimulated voltage command Vqfb on the basis of the d-axis secondsimulated current command Idff, the q-axis second simulated currentcommand Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; generation of the d-axis actual voltage commandVdref and the q-axis actual voltage command Vqref on the basis of thed-axis second simulated voltage command Vdff, the q-axis secondsimulated voltage command Vqff, the d-axis third simulated voltagecommand Vdfb, the q-axis third simulated voltage command Vqfb, thed-axis simulated disturbance voltage Vdob, and the q-axis simulateddisturbance voltage Vqob; and conversion of the d-axis voltage commandVdref and the q-axis actual voltage command Vqref into actual voltagecommands Vuref, Vvref, and Vwref on the basis of the actual position θof a rotor of the synchronous motor.

According to the method for controlling an electric current of asynchronous motor defined in claim 5, a current feedback gain can be setto a high level. Hence, even when variations arise in parameters orpower of the synchronous motor 1 and the power conversion circuit 4under the influence of temperature, a superior current responsecharacteristic can be obtained. Further, even when an abrupt change orfluctuation has arisen in a parameter of the synchronous motor land thatof the power conversion circuit 4, a superior current responsecharacteristic can be obtained. Moreover, a faster current responsecharacteristic can be obtained in response to the command.

A method for controlling an electric current of a synchronous motordefined in claim 6 is directed toward a method for controlling anelectric current of a synchronous motor in which a power conversioncircuit is provided with an appropriate actual voltage command such thatan electric current flowing through the synchronous motor fed with powerfrom the power conversion circuit coincides with a current command, themethod comprising: generation of a d-axis second simulated currentcommand Idff, a q-axis second simulated current command Iqff, a d-axissecond simulated voltage command Vdff, and a q-axis second simulatedvoltage command Vqff on the basis of a d-axis current command Idref anda q-axis current command Iqref; conversion of electric currents. Iu, Iv,and Iw flowing through the synchronous motor into a d-axis actualcurrent Idfb and a q-axis actual current Iqfb on rotational coordinateaxes which rotate synchronously with a rotor magnetic flux vector, onthe basis of an actual position θ of the rotor of the synchronous motor;estimation of a d-axis simulated current Idob, a q-axis simulatedcurrent Iqob, a d-axis simulated disturbance voltage Vdob, and a q-axissimulated disturbance voltage Vqob on the basis of the d-axis actualcurrent Idfb, the q-axis actual current Iqfb, a d-axis first simulatedvoltage command Vdo, and a q-axis actual voltage command Vqo; generationof a d-axis third simulated voltage command Vdfb and a q-axis thirdsimulated voltage command Vqfb on the basis of the d-axis secondsimulated current command Idff, the q-axis second simulated currentcommand Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; generation of the d-axis first simulated voltagecommand Vdo and the q-axis actual voltage command Vqo on the basis ofthe d-axis second simulated voltage command Vdff, the q-axis secondsimulated voltage command Vqff, the d-axis third simulated voltagecommand Vdfb, the q-axis third simulated voltage command Vqfb, thed-axis simulated disturbance voltage Vdob, and the q-axis simulateddisturbance voltage Vqob; addition of an induced voltage to the d-axisfirst simulated voltage command Vdo and the q-axis first simulatedvoltage command Vqo on the basis of the actual position θ of a rotor ofthe synchronous motor, to thereby produce a d-axis actual voltagecommand Vdref and a q-axis actual voltage command Vqref; and conversionof the d-axis voltage command Vdref and the q-axis actual voltagecommand Vqref into actual voltage commands Vuref, Vvref, and Vwref onthe basis of the actual position θ of a rotor of the synchronous motor.

According to the method for controlling an electric current of asynchronous motor defined in claim 6, a current feedback gain can be setto a high level. Hence, even when variations arise in parameters orpower of the synchronous motor 1 and the power conversion circuit 4under the influence of temperature, a superior current responsecharacteristic can be obtained. Further, even when an abrupt change orfluctuation has arisen in a parameter of the synchronous motor 1 andthat of the power conversion circuit 4, a superior current responsecharacteristic can be obtained. Moreover, a faster current responsecharacteristic can be obtained in response to the command. In addition,even when an abrupt change has arisen in the rotational speed of thesynchronous motor, a superior current response characteristic can beobtained.

A current controller of a synchronous motor defined in claim 7 isdirected toward a current controller of a synchronous motor in which apower conversion circuit 4 is provided with actual voltage commandsVuref, Vvref, and Vwref such that a d-axis actual current Idfb and aq-axis actual current Iqfb on rotational coordinate axes which rotatesynchronously with a rotor magnetic flux vector of a synchronous motor 1coincide with a d-axis current command Idref and a q-axis currentcommand Iqref, the controller comprising: an actual position observationdevice 2 for providing an actual position θ of the synchronous motor; anactual current observation section 3 which observes a current of twophases or more of the synchronous motor and provides actual currents Iu,Iv, and Iw; a second coordinate converter 6 which converts, on the basisof the actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; a current observer 10 awhich estimates a d-axis simulated current Idob and a q-axis simulatedcurrent Iqob on the basis of the d-axis actual current Idfb, the q-axisactual current Iqfb, a d-axis actual voltage command Vdref, and a q-axisactual voltage command Vqref; a feedback control section 9 a whichproduces the d-axis actual voltage command Vdref and the q-axis actualvoltage command Vqref on the basis of the d-axis current command Idref,the q-axis current command Iqref, the d-axis simulated current Idob, andthe q-axis simulated current Iqob; and a first coordinate converter 5for converting the d-axis actual voltage command Vdref and the q-axisactual voltage command Vqref into the actual voltage commands Vuref,Vvref, and Vwref on the basis of the actual position θ.

According to the current controller of a synchronous motor defined inclaim 7, a current feedback gain can be set to a high level. Hence, evenwhen variations arise in parameters and power of the synchronous motor 1and the power conversion circuit 4 under the influence of temperature, asuperior current response characteristic can be obtained.

A current controller of a synchronous motor defined in claim 8 isdirected toward a current controller of a synchronous motor in which apower conversion circuit 4 is provided with actual voltage commandsVuref, Vvref, and Vwref such that a d-axis actual current Idfb and aq-axis actual current Iqfb on rotational coordinate axes which rotatesynchronously with the rotor magnetic flux vector of a synchronous motor1 coincide with a d-axis current command Idref and a q-axis currentcommand Iqref, the controller comprising: an actual position observationdevice 2 for providing an actual position θ of the synchronous motor; anactual current observation section 3 which observes a current of twophases or more of the synchronous motor and provides actual currents Iu,Iv, and Iw; a second coordinate converter 6 which converts, on the basisof the actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; a current observer 10 bwhich estimates a d-axis simulated current Idob and a q-axis simulatedcurrent Iqob on the basis of the d-axis actual current Idfb, the q-axisactual current Iqfb, a d-axis first simulated voltage command Vdo, and aq-axis first simulated voltage command Vqo; a feedback control section 9b which produces the d-axis first simulated voltage command Vdo and theq-axis first simulated voltage command Vqo on the basis of the d-axiscurrent command Idref, the q-axis current command Iqref, the d-axissimulated current Idob, and the q-axis simulated current Iqob; a speedgenerator 8 for producing an actual speed “w” on the basis of the actualposition θ; an induced voltage compensation section 7 which adds aninduced voltage to the d-axis first simulated voltage command Vdo andthe q-axis first simulated voltage command Vqo on the basis of thed-axis first simulated voltage command Vdo, the q-axis first simulatedvoltage command Vqo, and the actual speed “w,” to thereby produce thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref; and a first coordinate converter 5 for converting thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref into the actual voltage commands Vuref, Vvref, and Vwrefon the basis of the actual position θ.

According to the current controller of a synchronous motor defined inclaim 8, a current feedback gain can be set to a high level. Hence, evenwhen variations arise in parameters or power of the synchronous motor 1and the power conversion circuit 4 under the influence of temperature, asuperior current response characteristic can be obtained. Further, evenwhen an abrupt change has arisen in the rotational speed of thesynchronous motor, a superior current response characteristic can beobtained.

A current controller of a synchronous motor defined in claim 9 isdirected toward a current controller of a synchronous motor in which apower conversion circuit 4 is provided with actual voltage commandsVuref, Vvref, and Vwref such that a d-axis actual current Idfb and aq-axis actual current Iqfb on rotational coordinate axes which rotatesynchronously with a rotor magnetic flux vector of a synchronous motor 1coincide with a d-axis current command Idref and a q-axis currentcommand Iqref, the controller comprising: an actual position observationdevice 2 for providing an actual position θ of the synchronous motor; anactual current observation section 3 which observes a current of twophases or more of the synchronous motor and provides actual currents Iu,Iv, and Iw; a second coordinate converter 6 which converts, on the basisof the actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; a current observer 10 bwhich estimates a d-axis simulated current Idob and a q-axis simulatedcurrent Iqob on the basis of the d-axis actual current Idfb, the q-axisactual current Iqfb, a d-axis first simulated voltage command Vdo, and aq-axis first simulated voltage command Vqo; a feedforward controlsection 12 which produces a d-axis second simulated current commandIdff, a q-axis second simulated current command Iqff, a d-axis secondsimulated voltage command Vdff, and a q-axis second simulated voltagecommand Vqff on the basis of the d-axis current command Idref and theq-axis current command Iqref; a feedback control section 11 whichproduces a d-axis third simulated voltage command Vdfb and a q-axisthird simulated voltage command Vqfb on the basis of the d-axis secondsimulated current command Idff, the q-axis second simulated currentcommand Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; a voltage command synthesizer 13 which producesthe d-axis first simulated voltage command Vdo and the q-axis firstsimulated voltage command Vqo on the basis of the d-axis third simulatedvoltage command Vdfb, the q-axis third simulated voltage command Vqfb,the d-axis second simulated voltage command Vdff, and the q-axis secondsimulated voltage command Vqff; a feedback control section 9 b whichproduces the d-axis first simulated voltage command Vdo and the q-axisfirst simulated voltage command Vqo on the basis of the d-axis currentcommand Idref, the q-axis current command Iqref, the d-axis simulatedcurrent Idob, and the q-axis simulated current Iqob; a speed generator 8for producing an actual speed “w” on the basis of the actual position θ;an induced voltage compensation section 7 which adds an induced voltageto the d-axis first simulated voltage command Vdo and the q-axis firstsimulated voltage command Vqo on the basis of the d-axis first simulatedvoltage command Vdo, the q-axis first simulated voltage command Vqo, andthe actual speed “w,” to thereby produce the d-axis actual voltagecommand Vdref and the q-axis actual voltage command Vqref; and a firstcoordinate converter 5 for converting the d-axis actual voltage commandVdref and the q-axis actual voltage command Vqref into the actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ.

According to the current controller of a synchronous motor defined inclaim 9, a current feedback gain can be set to a high level. Hence, evenwhen variations arise in parameters or power of the synchronous motor 1and the power conversion circuit 4 under the influence of temperature, asuperior current response characteristic can be obtained. Further, evenwhen an abrupt change has arisen in the rotational speed of thesynchronous motor, a superior current response characteristic can beobtained. Moreover, a faster current response characteristic in responseto the command can be obtained.

A current controller of a synchronous motor defined in claim 10 isdirected toward a current controller of a synchronous motor in which apower conversion circuit 4 is provided with actual voltage commandsVuref, Vvref, and Vwref such that a d-axis actual current Idfb and aq-axis actual current Iqfb on rotational coordinate axes which rotatesynchronously with the rotor magnetic flux vector of a synchronous motor1 coincide with a d-axis current command Idref and a q-axis currentcommand Iqref, the controller comprising: an actual position observationdevice 2 for providing an actual position θ of the synchronous motor; anactual current observation section 3 which observes a current of twophases or more of the synchronous motor and provides actual currents Iu,Iv, and Iw; a second coordinate converter 6 which converts, on the basisof the actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; a current observer 14 awhich estimates a d-axis simulated current Idob, a q-axis simulatedcurrent Iqob, a d-axis simulated disturbance voltage Vdob, and a q-axissimulated disturbance voltage Vqob on the basis of the d-axis actualcurrent Idfb, the q-axis actual current Iqfb, the d-axis actual voltagecommand Vdref, and the q-axis actual voltage command Vqref; a feedbackcontrol section 9 b which produces a d-axis first simulated voltagecommand Vdo and a q-axis first simulated voltage command Vqo on thebasis of the d-axis current command Idref, the q-axis current commandIqref, the d-axis simulated current Idob, and the q-axis simulatedcurrent Iqob; a voltage command synthesizer 15 which produces the d-axisactual voltage command Vdref and the q-axis actual voltage command Vqrefon the basis of the d-axis third simulated voltage command Vdfb, theq-axis third simulated voltage command Vqfb, the d-axis simulateddisturbance voltage Vdob, and the q-axis simulated disturbance voltageVqob; and a first coordinate converter 5 for converting the d-axisactual voltage command Vdref and the q-axis actual voltage command Vqrefinto the actual voltage commands Vuref, Vvref, and Vwref on the basis ofthe actual position θ.

According to the electric controller of a synchronous motor defined inclaim 10, a current feedback gain can be set to a high level. Hence,even when variations arise in parameters or power of the synchronousmotor 1 and the power conversion circuit 4 under the influence oftemperature, a superior current response characteristic can be obtained.Further, even when an abrupt change or fluctuation has arisen in aparameter of the synchronous motor 1 and that of the power conversioncircuit 4, a superior current response characteristic can be obtained.

A current controller of a synchronous motor defined in claim 11 isdirected toward a current controller of a synchronous motor whichprovides the power conversion circuit 4 with actual voltage commandsVuref, Vvref, and Vwref such that a d-axis actual current Idfb and aq-axis actual current Iqfb on rotational coordinate axes which rotatesynchronously with the rotor magnetic flux vector of a synchronous motor1 coincide with a d-axis current command Idref and a q-axis currentcommand Iqref, the controller comprising: an actual position observationdevice 2 for providing an actual position θ of the synchronous motor; anactual current observation section 3 which observes a current of twophases or more of the synchronous motor and provides actual currents Iu,Iv, and Iw; a second coordinate converter 6 which converts, on the basisof the actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb onrotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; a feedforward controlsection 12 which produces a d-axis second simulated current commandIdff, a q-axis second simulated current command Iqff, a d-axis secondsimulated voltage command Vdff, and a q-axis second simulated voltagecommand Vqff on the basis of the d-axis current command Idref and theq-axis current command Iqref; a current observer 14 a which estimates ad-axis simulated current Idob, a q-axis simulated current Iqob, a d-axissimulated disturbance voltage Vdob, and a q-axis simulated disturbancevoltage Vqob on the basis of the d-axis actual current Idfb, the q-axisactual current Iqfb, the d-axis actual voltage command Vdref, and theq-axis actual voltage command Vqref; a feedback control section 11 whichproduces a d-axis third simulated voltage command Vdfb and a d-axisthird simulated voltage command Vqfb on the basis of the d-axis secondsimulated current command Idff, the q-axis second simulated currentcommand Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; a voltage command synthesizer 16 which producesthe d-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref on the basis of the d-axis second simulated voltagecommand Vdff, the q-axis second simulated voltage command Vqff, thed-axis third simulated voltage command Vdfb, the q-axis third simulatedvoltage command Vqfb, the d-axis simulated disturbance voltage Vdob, andthe q-axis simulated disturbance voltage Vqob; and a first coordinateconverter 5 for converting the d-axis actual voltage command Vdref andthe q-axis actual voltage command Vqref into the actual voltage commandsVuref, Vvref, and Vwref on the basis of the actual position θ.

According to the electric controller of a synchronous motor defined inclaim 11, a current feedback gain can be set to a high level. Hence,even when variations arise in parameters or power of the synchronousmotor 1 and the power conversion circuit 4 under the influence oftemperature, a superior current response characteristic can be obtained.Further, even when an abrupt change or fluctuation has arisen in aparameter of the synchronous motor 1 and that of the power conversioncircuit 4, a superior current response characteristic can be obtained.Moreover, a faster current response characteristic can be obtained inresponse to the command.

A current controller of a synchronous motor defined in claim 12 isdirected toward a current controller of a synchronous motor in which apower conversion circuit 4 is provided with actual voltage commandsVuref, Vvref, and Vwref such that a d-axis actual current Idfb and aq-axis actual current Iqfb on rotational coordinate axes which rotatesynchronously with a rotor magnetic flux vector of a synchronous motor 1coincide with a d-axis current command Idref and a q-axis currentcommand Iqref, the controller comprising: an actual position observationdevice 2 for providing an actual position θ of the synchronous motor; anactual current observation section 3 which observes a current of twophases or more of the synchronous motor and provides actual currents Iu,Iv, and Iw; a second coordinate converter 6 which converts, on the basisof the actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; a feedforward controlsection 12 which produces a d-axis second simulated current commandIdff, a q-axis second simulated current command Iqff, a d-axis secondsimulated voltage command Vdff, and a q-axis second simulated voltagecommand Vqff on the basis of the d-axis current command Idref and theq-axis current command Iqref; a current observer 14 b which estimates ad-axis simulated current Idob, a q-axis simulated current Iqob, a d-axissimulated disturbance voltage Vdob, and a q-axis simulated disturbancevoltage Vqob on the basis of the d-axis actual current Idfb, the q-axisactual current Iqfb, a d-axis first simulated voltage command Vdo, and aq-axis actual voltage command Vqo; a feedback control section 11 whichproduces a d-axis third simulated voltage command Vdfb and a q-axisthird simulated voltage command Vqfb on the basis of the d-axis secondsimulated current command Idff, the q-axis second simulated currentcommand Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; a voltage command synthesizer 17 which producesthe d-axis first simulated voltage command Vdo and the q-axis actualvoltage command Vqo on the basis of the d-axis second simulated voltagecommand Vdff, the q-axis second simulated voltage command Vqff, thed-axis third simulated voltage command vdfb, and the q-axis thirdsimulated voltage command Vqfb; a speed generator 8 for producing anactual speed “w” on the basis of the actual position θ; an inducedvoltage compensation section 7 which adds an induced voltage to thed-axis first simulated voltage command Vdo and the q-axis firstsimulated voltage command Vqo on the basis of the d-axis first simulatedvoltage command Vdo, the q-axis first simulated voltage command Vqo, andthe actual speed “w,” to there by produce the d-axis actual voltagecommand Vdref and the q-axis actual voltage command Vqref; and a firstcoordinate converter 5 for converting the d-axis actual voltage commandVdref and the q-axis actual voltage command Vqref into the actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ.

According to the electric controller of a synchronous motor defined inclaim 12, a current feedback gain can be set to a high level. Hence,even when variations arise in parameters or power of the synchronousmotor 1 and the power conversion circuit 4 under the influence oftemperature, a superior current response characteristic can be obtained.Further, even when an abrupt change or fluctuation has arisen in aparameter of the synchronous motor land that of the power conversioncircuit 4, a superior current response characteristic can be obtained.Moreover, a faster current response characteristic can be obtained inresponse to the command. In addition, even when an abrupt change hasarisen in the rotational speed of the synchronous motor, a superiorcurrent response characteristic can be obtained.

In order to achieve the second object, an invention which is defined inclaim 13 and pertains to a method for controlling a synchronous motor isdirected toward a method for controlling a synchronous motor in which apower conversion circuit is provided with appropriate actual voltagecommands Vuref, Vvref, and Vwref such that a synchronous motor fed withpower from the power conversion circuit approaches an actual commandθref, the method comprising: performance of machine control operation onthe basis of the actual command θref, the actual position θ of a rotorof the synchronous motor, and an estimated speed “w,” to thereby providea torque command Tref; conversion of electric currents Iu, Iv, and Iwflowing through the synchronous motor into a d-axis actual current Idand a q-axis actual current Iq on rotational coordinate axes whichrotate synchronously with a rotor magnetic flux vector, on the basis ofan actual position θ of the rotor of the synchronous motor; performanceof current control operation on the basis of the actual position θ, thetorque command Tref, the d-axis actual current Id, and the q-axis actualcurrent Iq, to thereby provide a d-axis voltage command Vdref and aq-axis voltage command Vqref; conversion of the d-axis voltage commandVdref and the q-axis voltage command Vqref into actual voltage commandsVuref, Vvref, and Vwref on the basis of the actual position θ; andestimation of an estimated speed “w” on the basis of the q-axis actualcurrent Iq and the q-axis voltage command Vqref.

According to the method for controlling a synchronous motor, even whenthe sampling time is shortened, superior readiness and superiorrobustness can be obtained without involvement of an increase in theresolving power of an encoder.

An invention which is defined in claim 14 and pertains to a method forcontrolling a synchronous motor is directed toward a method forcontrolling a synchronous motor in which a power conversion circuit isprovided with appropriate actual voltage commands Vuref, Vvref, andVwref such that a synchronous motor fed with power from the powerconversion circuit approaches an actual command θref, the methodcomprising: performance of machine control operation on the basis of theactual command θref, the actual position θ of a rotor of the synchronousmotor, and an estimated speed “w,” to thereby provide a torque commandTref; conversion of electric currents Iu, Iv, and Iw flowing through thesynchronous motor into a d-axis actual current Id and a q-axis actualcurrent Iq on rotational coordinate axes which rotate synchronously witha rotor magnetic flux vector, on the basis of an actual position θ ofthe rotor of the synchronous motor; performance of current controloperation on the basis of the actual position θ, the torque commandTref, the d-axis actual current Id, and the q-axis actual current Iq, tothereby provide a d-axis voltage command Vdref and a q-axis voltagecommand Vqref; conversion of the d-axis voltage command Vdref and theq-axis voltage command Vqref into actual voltage commands Vuref, Vvref,and Vwref on the basis of the actual position θ; and estimation of anestimated speed “w” on the basis of the d-axis actual current Id, theq-axis actual current Iq, the d-axis voltage command Vdref, and theq-axis voltage command Vqref.

According to the method for controlling a synchronous motor, even whenthe sampling time is shortened, superior readiness and superiorrobustness can be obtained without involvement of an increase in theresolving power of an encoder. In addition, the accuracy of theestimated speed “w” becomes higher. Hence, a control gain of the machinecontrol section can be set to a high level.

An invention which is defined in claim 15 and pertains to a currentcontroller of a synchronous motor is directed toward a currentcontroller of a synchronous motor in which a power conversion circuit 84is provided with appropriate actual voltage commands Vuref, Vvref, andVwref such that a synchronous motor 81 fed with power from the powerconversion circuit 84 approaches an actual command θref, the controllercomprising: an actual position observation device 82 for providing anactual position θ of the synchronous motor 81; an actual currentobservation section 83 which observes a current of two phases or more ofthe synchronous motor 81 and provides actual currents Iu, Iv, and Iw; afirst coordinate conversion circuit 86 which converts, on the basis ofthe actual position θ, the actual currents Iu, Iv, and Iw into a d-axisactual current Id and a q-axis actual current Iq on the rotationalcoordinate axes which rotate synchronously with the rotor magnetic fluxvector of the synchronous motor; a machine control section 88 whichperforms machine control operation, to thereby provide a torque commandTref on the basis of the actual command θref, the actual position θ of arotor of the synchronous motor, and the estimated speed “w”; a currentcontrol section 87 which performs current control operation on the basisof the torque command Tref, the d-axis actual current Id, the q-axisactual current Iq, and the actual position θ, to thereby provide ad-axis voltage command Vdref and a q-axis voltage command Vqref; asecond coordinate conversion circuit 85 which provides the actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ, the d-axis voltage command Vdref, and the q-axis voltagecommand Vqref; and a first speed estimation section 89 for estimatingthe estimated speed “w” on the basis of the q-axis actual current Iq andthe q-axis voltage command Vqref.

According to the controller of a synchronous motor, even when thesampling time is shortened, superior readiness and superior robustnesscan be obtained without involvement of an increase in the resolvingpower of an encoder.

An invention which is defined in claim 16 and pertains to a currentcontroller of a synchronous motor is directed toward a currentcontroller of a synchronous motor in which a power conversion circuit 84is provided with appropriate actual voltage commands Vuref, Vvref, andVwref such that a synchronous motor 81 fed with power from the powerconversion circuit 84 approaches an actual command θref, the controllercomprising: an actual position observation device 82 for providing anactual position θ of the synchronous motor 81; an actual currentobservation section 83 which observes a current of two phases or more ofthe synchronous motor 81 and provides actual currents Iu, Iv, and Iw; afirst coordinate conversion circuit 86 which converts, on the basis ofthe actual position θ, the actual currents Iu, Iv, and Iw into a d-axisactual current Id and a q-axis actual current Iq on the rotationalcoordinate axes which rotate synchronously with the rotor magnetic fluxvector of the synchronous motor; a machine control section 88 whichperforms machine control operation, to thereby provide the torquecommand Tref on the basis of the actual command θref, the actualposition θ of the rotor of the synchronous motor, and the estimatedspeed “w”; a current control section 87 which performs current controloperation on the basis of the torque command Tref, the d-axis actualcurrent Id, the q-axis actual current Iq, and the actual position θ, tothereby provide a d-axis voltage command Vdref and a q-axis voltagecommand Vqref; a second coordinate conversion circuit 85 which providesthe actual voltage commands Vuref, Vvref, and Vwref on the basis of theactual position θ, the d-axis voltage command Vdref, and the q-axisvoltage command Vqref; and a second speed estimation section 90 forestimating the estimated speed “w” on the basis of the d-axis actualcurrent Id, the q-axis actual current Iq, the d-axis voltage commandVdref, and the q-axis voltage command Vqref.

According to the controller of a synchronous motor, even when thesampling time is shortened, superior readiness and superior robustnesscan be obtained without involvement of an increase in the resolvingpower of an encoder. Moreover, the accuracy of the estimated speed “w”becomes higher, and hence a control gain of the machine control sectioncan be set to a high level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the configuration of a currentcontroller of a synchronous motor according to a first embodiment of theinvention;

FIG. 2 is a block diagram showing the configuration of a currentcontroller of a synchronous motor according to a second embodiment ofthe invention;

FIG. 3 is a block diagram showing the configuration of a currentcontroller of a synchronous motor according to a third embodiment of theinvention;

FIG. 4 is a block diagram showing the configuration of a currentcontroller of a synchronous motor according to a fourth embodiment ofthe invention;

FIG. 5 is a block diagram showing the configuration of a currentcontroller of a synchronous motor according to a fifth embodiment of theinvention;

FIG. 6 is a block diagram showing the configuration of a currentcontroller of a synchronous motor according to a sixth embodiment of theinvention;

FIG. 7 is a block diagram showing the configuration of a related-artmotor controller;

FIG. 8 is a block diagram showing the configuration of a currentcontroller of a synchronous motor according to a seventh embodiment ofthe invention;

FIG. 9 is a block diagram showing the configuration of a currentcontroller of a synchronous motor according to an eighth embodiment ofthe invention; and

FIG. 10 is a block diagram showing the configuration of a motorcontroller of a related-art synchronous motor.

In the drawings, reference numeral 1 designates a synchronous motor; 2designates an actual position observation device; 3 designates an actualcurrent observation section; 4 designates a power conversion circuit; 5designates a first coordinate converter; 6 designates a secondcoordinate converter; 7 designates an induced voltage compensationsection; 8 designates a speed generation section; 9 a designates acurrent feedback control section; 9 b designates a current feedbackcontrol section; 10 a designates a current observer; 10 b designates acurrent observer; 11 designates a feedback control section; 12designates a feedforward control section; 13 designates a voltagecommand synthesis section; 14 a designates a current observer; 14 bdesignates a current observer; 15 designates a voltage command synthesissection; 16 designates a voltage command synthesis section; 17designates a voltage command synthesis section; 20 designates a feedbackcontrol section; 81 designates a synchronous motor; 82 designates anactual observation device; 83 designates an actual current observationsection; 84 designates a power conversion circuit; 85 designates asecond coordinate converter; 86 designates a first coordinate converter;87 designates a current control section; 88 designates a machine controlsection; 89 designates a first speed estimation section; 90 designates asecond speed estimation section; and 91 designates a differentiator.

BEST MODES FOR CARRYING OUT THE INVENTION

In relation to the invention intended for achieving the first objective,first through sixth embodiments (FIGS. 1 through 6) are described. Inrelation to the invention intended for achieving the second objective,seventh and eighth embodiments (FIGS. 8 and 9) are described.

First, a method and apparatus for controlling an electric current of asynchronous motor according to a first embodiment of the invention willbe described by reference to FIG. 1.

The current controller of the synchronous motor hereinafter correspondsto an embodiment of a method for controlling a synchronous motor.

As shown in FIG. 1, in the current controller of the synchronous motoraccording to the embodiment, a power conversion circuit 4 is providedwith actual voltage commands Vuref, Vvref, and Vwref such that a d-axisactual current Idfb and a q-axis actual current Iqfb on rotationalcoordinate axes which rotate synchronously with a rotor magnetic fluxvector of the synchronous motor 1 coincide with a d-axis current commandIdref and a q-axis current command Iqref, and the controller comprises:an actual position observation device 2 for providing an actual positionθ of the synchronous motor; an actual current observation section 3which observes a current of two phases or more of the synchronous motorand provides actual currents Iu, Iv, and Iw; a second coordinateconverter 6 which converts, on the basis of the actual position θ, theactual currents Iu, Iv, and Iw into the d-axis actual current Idfb andthe q-axis actual current Iqfb on the rotational coordinate axes whichrotate synchronously with the rotor magnetic flux vector of thesynchronous motor; a current observer 10 a which estimates a d-axissimulated current Idob and a q-axis simulated current Iqob on the basisof the d-axis actual current Idfb, the q-axis actual current Iqfb, ad-axis actual voltage command Vdref, and a q-axis actual voltage commandVqref; a feedback control section 9 a which produces the d-axis actualvoltage command Vdref and the q-axis actual voltage command Vqref on thebasis of the d-axis current command Idref, the q-axis current commandIqref, the d-axis simulated current Idob, and the q-axis simulatedcurrent Iqob; and a first coordinate converter 5 for converting thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref into the actual voltage commands Vuref, Vvref, and Vwrefon the basis of an actual position θ of a rotor of the synchronousmotor.

The synchronous motor 1, the actual position observation device 2, theactual current observation section 3, the power conversion circuit 4,the first coordinate converter 5, and the second coordinate converter 6are identical with related-art devices.

The current observer 10 a generates the d-axis simulated current Idoband the q-axis simulated current Iqob in the following manner. Here, “s”designates a differential operator; Rd designates d-axis equivalentresistance; Rq designates q-axis equivalent resistance; Ld designatesd-axis equivalent inductance; and Lq designates q-axis equivalentinductance. Ld1, Ld2, Lq1, and Lq2 designate gains of the currentobserver that should be set in a pole assignment.Idob*s=−Rd*Idob/Ld+Ld 1*(Idfb−Idob)+(Vdob+Vdref)/Ld  (1)Vdob*s=Ld 2*(Idfb−Idob)  (2)Iqob*s=−Rq*Iqob/Lq+Lq 1*(Iqfb−Iqob)+(Vqob+Vqref)/Lq  (3)Vqob*s=Lq 2*(Iqfb−Iqob)  (4)

The feedback control section 9 a produces the d-axis actual voltagecommand Vdref and the q-axis actual voltage command Vqref in thefollowing manner, where kda and kqa designate feedback gains.Vdref=kda*(Idref−Idob)  (5)Vqref=kqa*(Iqref−Iqob)  (6)

According to the current controller of the synchronous motor of thefirst embodiment, feedback control is performed by use of the d-axissimulated current Idob and the q-axis simulated current Iqob, both beingproduced by the current observer section 1 a, in place of measuredcurrents Idfb and Iqfb, thereby suppressing noise included in themeasured currents Idfb, Iqfb and enabling setting of the feedback gainskda and kqa to high levels. Hence, even when variations arise inparameters or power of the synchronous motor 1 and the power conversioncircuit 4 under the influence of temperature, a superior currentresponse characteristic can be obtained.

Here, the feedback control section 9 a may be configured by means ofproportional/integral control rather than proportional controlrepresented by Equations (5), (6). Moreover, the current observer 10 amay be configured in consideration of interference components of the d,q axes.

A current controller of a synchronous motor according to a secondembodiment of the invention will be described by reference to FIG. 2.

As shown in FIG. 2, in the current controller of the synchronous motoraccording to the embodiment, the power conversion circuit 4 is providedwith the actual voltage commands Vuref, Vvref, and Vwref such that thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor 1 coincide with the d-axiscurrent command Idref and the q-axis current command Iqref, and thecontroller comprises: the actual position observation device 2 forproviding an actual position θ of the synchronous motor; the actualcurrent observation section 3 which observes a current of two phases ormore of the synchronous motor and provides actual currents Iu, Iv, andIw; the second coordinate converter 6 which converts, on the basis ofthe actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; the current observer 10 bwhich estimates the d-axis simulated current Idob and the q-axissimulated current Iqob on the basis of the d-axis actual current Idfb,the q-axis actual current Iqfb, a d-axis first simulated voltage commandVdo, and a q-axis first simulated voltage command Vqo; the currentfeedback control section 9 b which produces the d-axis first simulatedvoltage command Vdo and the q-axis first simulated voltage command Vqoon the basis of the d-axis current command Idref, the q-axis currentcommand Iqref, the d-axis simulated current Idob, and the q-axissimulated current Iqob; the speed generator 8 for producing an actualspeed “w” on the basis of the actual position θ; an induced voltagecompensation section 7 which adds an induced voltage to the d-axis firstsimulated voltage command Vdo and the q-axis first simulated voltagecommand Vqo on the basis of the d-axis first simulated voltage commandVdo, the q-axis first simulated voltage command Vqo, and the actualspeed “w;” to thereby produce the d-axis actual voltage command Vdrefand the q-axis actual voltage command Vqref; and the first coordinateconverter 5 for converting the d-axis actual voltage command Vdref andthe q-axis actual voltage command Vqref into the actual voltage commandsVuref, Vvref, and Vwref on the basis of the actual position θ.

The current observer 10 b generates the d-axis simulated current Idoband the q-axis simulated current Iqob as follows.Idob*s=−Rd*Idob/Ld+Ld 1*(Idfb−Idob)+(Vdob+Vdo)/Ld  (7)Vdob*s=Ld 2*(Idfb−Idob)  (8)Iqob*s=−Rq*Iqob/Lq+Lq 1*(Iqfb−Iqob)+(Vqob+Vqo)/Lq  (9)Vqob*s=Lq 2*(Iqfb−Iqob)  (10)

The feedback control section 9 b produces the d-axis first simulatedvoltage command Vdo and the q-axis first simulated voltage command Vqoin the following manner, where kda and kqa designate feedback gains.Vdo=kda*(Idref−Idob)  (11) Vqo=kqa*(Iqref−Iqob)  (12)The speed generator 8 generates the actual speed “w” as follows.w=s*θ  (13)

The induced voltage compensation section 7 produces the d-axis actualvoltage command Vdref and the q-axis voltage command Vqref as follows,where φd represents a d-axis equivalent magnetic flux coefficient, andφq represents a q-axis equivalent magnetic flux coefficient.Vdref=d*w  (14)Vqref=Vqo+φq*w  (15)

According to the current controller of the synchronous motor of thesecond embodiment, feedback control is performed by use of the d-axissimulated current Idob and the q-axis simulated current Iqob, both beingproduced by the current observer section 10 b, in place of the measuredcurrents Idfb and Iqfb, thereby suppressing noise included in themeasured currents Idfb, Iqfb and enabling setting of the feedback gainskda and kqa to high levels. Hence, even when variations arise inparameters or power of the synchronous motor 1 and the power conversioncircuit 4 under the influence of temperature, a superior currentresponse characteristic can be obtained. Further, when an abrupt changearises in the rotational speed of the synchronous motor, estimationerrors in the d-axis simulated current Idob and the q-axis simulatedcurrent Iqob, both being produced by the current observer section 10 b,are suppressed by compensating for the induced voltage on the basis ofthe induced voltage compensation section 7. Accordingly, even when anabrupt change arises in the rotational speed of the synchronous motor, asuperior current response characteristic can be obtained.

Here, the feedback control section 9 b may be configured by means ofproportional/integral control rather than proportional controlrepresented by Equations (11), (12).

Moreover, the current observer 10 b may be configured in considerationof interference components of the d, q axes.

A current controller of a synchronous motor according to a thirdembodiment of the invention will be described by reference to FIG. 3.

As shown in FIG. 3, in the current controller of the synchronous motoraccording to the embodiment, the power conversion circuit 4 is providedwith the voltage commands Vuref, Vvref, and Vwref such that the d-axisactual current Idfb and the q-axis actual current Iqfb on the rotationalcoordinate axes which rotate synchronously with the rotor magnetic fluxvector of the synchronous motor 1 coincide with the d-axis currentcommand Idref and the q-axis current command Iqref, and the controllercomprises: the actual position observation device 2 for providing anactual position θ of the synchronous motor; the actual currentobservation section 3 which observes a current of two phases or more ofthe synchronous motor and provides actual currents Iu, Iv, and Iw; thesecond coordinate converter 6 which converts, on the basis of the actualposition θ, the actual currents Iu, Iv, and Iw into the d-axis actualcurrent Idfb and the q-axis actual current Iqfb on the rotationalcoordinate axes which rotate synchronously with the rotor magnetic fluxvector of the synchronous motor; the current observer 10 b whichestimates the d-axis simulated current Idob and the q-axis simulatedcurrent Iqob on the basis of the d-axis actual current Idfb, the q-axisactual current Iqfb, the d-axis first simulated voltage command Vdo, andthe q-axis first simulated voltage command Vqo; a feedforward controlsection 12 which produces a d-axis second simulated current commandIdff, a q-axis second simulated current command Iqff, a d-axis secondsimulated voltage command Vdff, and a q-axis second simulated voltagecommand Vqff on the basis of the d-axis current command Idref and theq-axis current command Iqref; a feedback control section 11 whichproduces a d-axis third simulated voltage command Vdfb and a q-axisthird simulated voltage command Vqfb on the basis of the d-axis secondsimulated current command Idff, the q-axis second simulated currentcommand Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; a voltage command synthesizer 13 which producesthe d-axis first simulated voltage command Vdo and the q-axis firstsimulated voltage command Vqo on the basis of the d-axis third simulatedvoltage command Vdfb, the q-axis third simulated voltage command Vqfb,the d-axis second simulated voltage command Vdff, and the q-axis secondsimulated voltage command Vqff; a current feedback control section 9 bwhich produces the d-axis first simulated voltage command Vdo and theq-axis first simulated voltage command Vqo on the basis of the d-axiscurrent command Idref, the q-axis current command Iqref, the d-axissimulated current Idob, and the q-axis simulated current Iqob; the speedgenerator 8 for producing the actual speed “w” on the basis of theactual position θ; the induced voltage compensation section 7 which addsan induced voltage to the d-axis first simulated voltage command Vdo andthe q-axis first simulated voltage command Vqo on the basis of thed-axis first simulated voltage command Vdo, the q-axis first simulatedvoltage command Vqo, and the actual speed“w,” to thereby produce thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref; and the first coordinate converter 5 for converting thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref into the actual voltage commands Vuref, Vvref, and Vwrefon the basis of the actual position θ.

The feedforward control section 12 produces the d-axis simulated currentcommand Idff, the q-axis second simulated current command Iqff, thed-axis second simulated voltage command Vdff, and the q-axis secondsimulated voltage command Vqff in the following manner. Here, kdf, Kqfdenote control gains of the feedforward control section 12.Idff*s=−Rd*Idff/Ld+Vdff  (16)Vdff=Kdf*(Idref−Idff)  (17)Iqff*s=−Rq*Iqff/Lq+Vqff  (18)Vqff=Kqf*(Iqref−Iqff)  (19)

The feedback control section 11 produces the d-axis third simulatedvoltage command Vdfb and the q-axis third simulated voltage command Vqfbin the following manner.Vdfb=kda*(Idff−Idob)  (20)Vqfb=kqa*(Iqff−Iqob)  (21)

The voltage command synthesizer 13 produces the d-axis first simulatedvoltage command Vdo and the q-axis first simulated voltage command Vqoin the following manner.Vdo=Vdfb+Vdff  (22)Vqo=Vqfb+Vqff  (23)

According to the current controller of the synchronous motor of thethird embodiment, feedback control is performed by use of the d-axissimulated current Idob and the q-axis simulated current Iqob, both beingproduced by the current observer section 10 b, in place of the measuredcurrents Idfb and Iqfb, thereby suppressing noise included in themeasured currents Idfb, Iqfb and enabling setting of the feedback gainskda and kqa to high levels. Hence, even when variations arise inparameters or power of the synchronous motor 1 and the power conversioncircuit 4 under the influence of temperature, a superior currentresponse characteristic can be obtained. Further, when an abrupt changearises in the rotational speed of the synchronous motor, estimationerrors in the d-axis simulated current Idob and the q-axis simulatedcurrent Iqob, both being produced by the current observer section 10 a,can be suppressed by compensating for the induced voltage on the basisof the induced voltage compensation section 7. Accordingly, even when anabrupt change arises in the rotational speed of the synchronous motor, asuperior current response characteristic can be obtained. Still further,a faster current response characteristic in response to the command canbe obtained, by inputting the d-axis second simulated voltage commandVdff and the q-axis second simulated voltage command Vqff, both beingproduced by the feedforward control section 12, directly to the voltagecommand synthesizer 13.

Here, the feedback control section 11 may be configured by means ofproportional/integral control rather than proportional controlrepresented by Equations (20), (21).

A current controller of a synchronous motor according to a fourthembodiment of the invention will be described by reference to FIG. 4.

As shown in FIG. 4, in the current controller of the synchronous motoraccording to the embodiment, the power conversion circuit 4 is providedwith the actual voltage commands Vuref, Vvref, and Vwref such that thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor 1 coincide with the d-axiscurrent command Idref and the q-axis current command Iqref, and thecontroller comprises: the actual position observation device 2 forproviding an actual position θ of the synchronous motor; the actualcurrent observation section 3 which observes a current of two phases ormore of the synchronous motor and provides actual currents Iu, Iv, andIw; the second coordinate converter 6 which converts, on the basis ofthe actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; the current observer 14 awhich estimates a d-axis simulated current Idob, a q-axis simulatedcurrent Iqob, a d-axis simulated disturbance voltage Vdob, and a q-axissimulated disturbance voltage Vqob on the basis of the d-axis actualcurrent Idfb, the q-axis actual current Iqfb, the d-axis actual voltagecommand Vdref, and the q-axis actual voltage command Vqref; the feedbackcontrol section 9 b which produces the d-axis first simulated voltagecommand Vdo and the q-axis first simulated voltage command Vqo on thebasis of the d-axis current command Idref, the q-axis current commandIqref, the d-axis simulated current Idob, and the q-axis simulatedcurrent Iqob; the voltage command synthesizer 15 which produces thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref on the basis of the d-axis third simulated voltage commandVdfb, the q-axis third simulated voltage command Vqfb, the d-axissimulated disturbance voltage Vdob; and the q-axis simulated disturbancevoltage Vqob; and the first coordinate converter 5 for converting thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref into the actual voltage commands Vuref, Vvref, and Vwrefon the basis of the actual position θ.

The current observer 14 a generates the d-axis simulated current Idob,the q-axis simulated current Iqob, the d-axis simulated disturbancevoltage Vdob, and the q-axis simulated disturbance voltage Vqob asfollows.Idob*s=−Rd*Idob/Ld+Ld 1*(Idfb−Idob)+(Vdob+Vdref)/Ld  (24)Vdob*s=Ld 2*(Idfb−Idob)  (25)Iqob*s=−Rq*Iqob/Lq+Lq 1*(Iqfb−Iqob)+(Vqob+Vqref)/Lq  (26)Vqob*s=Lq 2*(Iqfb−Iqob)  (27)

The voltage command synthesizer 15 produces the d-axis actual voltagecommand Vdref and the q-axis actual voltage command Vqref as follows:Vdref=Vdob+Vdo  (28)Vqref=Vqob+Vqo  (29)

According to the current controller of the synchronous motor of thefourth embodiment, feedback control is performed by use of the d-axissimulated current Idob and the q-axis simulated current Iqob, both beingproduced by the current observer section 14 a, in place of the measuredcurrents Idfb and Iqfb, thereby suppressing noise included in themeasured currents Idfb, Iqfb and enabling setting of the feedback gainskda and kqa to high levels. Hence, even when variations arise inparameters or power of the synchronous motor 1 and the power conversioncircuit 4 under the influence of temperature, a superior currentresponse characteristic can be obtained. A disturbance voltage componentcan be compensated by inputting the d-axis simulated disturbance voltageVdob and the q-axis simulated disturbance voltage Vqob, both beingproduced by the current observer section 14 a, directly to the voltagecommand synthesizer 15. Accordingly, even when abrupt changes havearisen in parameters or power of the synchronous motor 1 and the powerconversion circuit 4, a superior current response characteristic can beobtained. Further, the current observer 14 a maybe constructed inconsideration of the d-axis and q-axis interference components.

A current controller of a synchronous motor according to a fifthembodiment of the invention will be described by reference to FIG. 5.

As shown in FIG. 5, in the current controller of the synchronous motoraccording to the embodiment, the power conversion circuit 4 is providedwith the actual voltage commands Vuref, Vvref, and Vwref such that thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor 1 coincide with thed-axis-current command Idref and the q-axis current command Iqref, andthe controller comprises: the actual position observation device 2 forproviding an actual position θ of the synchronous motor; the actualcurrent observation section 3 which observes a current of two phases ormore of the synchronous motor and provides actual currents Iu, Iv, andIw; the second coordinate converter 6 which converts, on the basis ofthe actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; the feedforward controlsection 12 which produces the d-axis second simulated current commandIdff, the q-axis second simulated current command Iqff, the d-axissecond simulated voltage command Vdff, and the q-axis second simulatedvoltage command Vqff on the basis of the d-axis current command Idrefand the q-axis current command Iqref; the current observer 14 a whichestimates the d-axis simulated current Idob, the q-axis simulatedcurrent Iqob, the d-axis simulated disturbance voltage Vdob, and theq-axis simulated disturbance voltage Vqob on the basis of the d-axisactual current Idfb, the q-axis actual current Iqfb, the d-axis actualvoltage command Vdref, and the q-axis actual voltage command Vqref; thefeedback control section 11 which produces the d-axis third simulatedvoltage command Vdfb and the q-axis third simulated voltage command Vqfbon the basis of the d-axis second simulated current command Idff, theq-axis second simulated current command Iqff, the d-axis simulatedcurrent Idob, and the q-axis simulated current Iqob; the voltage commandsynthesizer 16 which produces the d-axis actual voltage command Vdrefand the q-axis actual voltage command Vqref on the basis of the d-axissecond simulated voltage command Vdff, the q-axis second simulatedvoltage command Vqff, the d-axis third simulated voltage command Vdfb,the q-axis third simulated voltage command Vqfb, the d-axis simulateddisturbance voltage Vdob, and the q-axis simulated disturbance voltageVqob; and the first coordinate converter 5 for converting the d-axisactual voltage command Vdref and the q-axis actual voltage command Vqrefinto the actual voltage commands Vuref, Vvref, and Vwref on the basis ofthe actual position θ.

The voltage command synthesizer 16 produces the d-axis actual voltagecommand Vdref and the q-axis actual voltage command Vqref as follows.Vdref=Vdob+Vdfb+Vdff  (30) Vqref=Vqob+Vqfb+Vqff  (31)

According to the current controller of the synchronous motor of thefifth embodiment, feedback control is performed by use of the d-axissimulated current Idob and the q-axis simulated current Iqob, both beingproduced by the current observer section 14 a, in place of the measuredcurrents Idfb and Iqfb, thereby suppressing noise included in themeasured currents Idfb, Iqfb and enabling setting of the feedback gainskda and kqa to high levels. Hence, even when variations arise inparameters or power of the synchronous motor 1 and the power conversioncircuit 4 under the influence of temperature, a superior currentresponse characteristic can be obtained. A disturbance voltage componentcan be compensated by inputting the d-axis simulated disturbance voltageVdob and the q-axis simulated disturbance voltage Vqob, both beingproduced by the current observer section 14 a, directly to the voltagecommand synthesizer 16. Accordingly, even when abrupt changes havearisen in parameters or power of the synchronous motor 1 and the powerconversion circuit 4, a superior current response characteristic can beobtained. Moreover, the d-axis second simulated voltage command Vdff andthe q-axis second simulated voltage command Vqff, both being produced bythe feedforward control section 12, are input directly to the voltagecommand synthesizer 16, thereby providing a faster current responsecharacteristic in response to the command.

A current controller of a synchronous motor according to a sixthembodiment of the invention will be described by reference to FIG. 6.

As shown in FIG. 6, in the current controller of the synchronous motoraccording to the embodiment, the power conversion circuit 4 is providedwith the actual voltage commands Vuref, Vvref, and Vwref such that thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor 1 coincide with the d-axiscurrent command Idref and the q-axis current command Iqref, and thecontroller comprises: the actual position observation device 2 forproviding an actual position θ of the synchronous motor; the actualcurrent observation section 3 which observes a current of two phases ormore of the synchronous motor and provides actual currents Iu, Iv, andIw; the second coordinate converter 6 which converts, on the basis ofthe actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; the feedforward controlsection 12 which produces the d-axis second simulated current commandIdff, the q-axis second simulated current command Iqff, the d-axissecond simulated voltage command Vdff, and the q-axis second simulatedvoltage command Vqff on the basis of the d-axis current command Idrefand the q-axis current command Iqref; the current observer 14 b whichestimates the d-axis simulated current Idob, the q-axis simulatedcurrent Iqob, the d-axis simulated disturbance voltage Vdob, and theq-axis simulated disturbance voltage Vqob on the basis of the d-axisactual current Idfb, the q-axis actual current Iqfb, the d-axis firstsimulated voltage command Vdo, and the q-axis actual voltage commandVqo; the feedback control section 11 which produces the d-axis thirdsimulated voltage command Vdfb, the q-axis third simulated voltagecommand Vqfb, the d-axis simulated disturbance voltage Vdob, and theq-axis simulated disturbance voltage Vqob on the basis of the d-axissecond simulated current command Idff, the q-axis second simulatedcurrent command Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; a voltage command synthesizer 17 which producesthe d-axis first simulated voltage command Vdo and the q-axis firstsimulated voltage command Vqo on the basis of the d-axis secondsimulated voltage command Vdff, the q-axis second simulated voltagecommand Vqff, the d-axis third simulated voltage command Vdfb, theq-axis third simulated voltage command Vqfb, the d-axis simulateddisturbance voltage Vdob, and the q-axis simulated disturbance voltageVqob; the speed generator 8 for producing the actual speed “w” on thebasis of the actual position θ; the induced voltage compensation section7 which adds an induced voltage to the d-axis first simulated voltagecommand Vdo and the q-axis first simulated voltage command Vqo on thebasis of the d-axis first simulated voltage command Vdo, the q-axisfirst simulated voltage command Vqo, and the actual speed “w,” tothereby produce the d-axis actual voltage command Vdref and the q-axisactual voltage command Vqref; and the first coordinate converter 5 forconverting the d-axis actual voltage command Vdref and the q-axis actualvoltage command Vqref into the actual voltage commands Vuref, Vvref, andVwref on the basis of the actual position θ.

The current observer 14 b generates the d-axis simulated current Idob,the q-axis simulated current Iqob, the d-axis simulated disturbancevoltage Vdob, and the q-axis simulated disturbance voltage Vqob asfollows.Idob*s=−Rd*Idob/Ld+Ld 1*(Idfb−Idob)+(Vdob+Vdo)/Ld  (32)Vdob*s=Ld 2*(Idfb−Idob)  (33)Iqob*s=−Rq*Iqob/Lq+Lq 1*(Iqfb−Iqob)+(Vqob+Vqo)/Lq  (34)Vqob*s=Lq 2*(Iqfb−Iqob)  (35)

The voltage command synthesizer 17 produces the d-axis actual voltagecommand Vdref and the actual voltage command Vqref as follows:Vdo=Vdff+Vdfb+Vdob  (36)Vqo=Vqff+Vqfb+Vqob  (37).

According to the current controller of the synchronous motor of thesixth embodiment, feedback control is performed by use of the d-axissimulated current Idob and the q-axis simulated current Iqob, both beingproduced by the current observer section 14 b, in place of the measuredcurrents Idfb and Iqfb, thereby suppressing noise included in themeasured currents Idfb, Iqfb and enabling setting of the feedback gainskda and kqa to high levels. Hence, even when variations arise inparameters or power of the synchronous motor 1 and the power conversioncircuit 4 under the influence of temperature, a superior currentresponse characteristic can be obtained. A disturbance voltage componentcan be compensated by inputting the d-axis simulated disturbance voltageVdob and the q-axis simulated disturbance voltage Vqob, both beingproduced by the current observer section 14 b, directly to the voltagecommand synthesizer 15. Accordingly, even when abrupt changes havearisen in parameters or power of the synchronous motor 1 and the powerconversion circuit 4, a superior current response characteristic can beobtained. Further, a faster current response characteristic in responseto the command can be obtained, by inputting the d-axis second simulatedvoltage command Vdff and the q-axis second simulated voltage commandVqff, both being produced by the feedforward control section 12,directly to the voltage command synthesizer 16. Moreover, when abruptchanges have arisen in the rotational speed of the synchronous motor, anestimation error in the d-axis simulated current Idob and that in theq-axis simulated current Iqob, both being produced by the currentobserver section 14 b, are suppressed by compensating for the inducedvoltage by means of the induced voltage compensation section 7. As aresult, even when an abrupt change has arisen in the rotational speed ofthe synchronous motor, a superior current response characteristic can beobtained. Further, the current observer 14 b may be constructed inconsideration of the d-axis interference component and the q-axisinterference component.

An apparatus and method for controlling a synchronous motor according toa seventh embodiment of the invention will be described by reference toFIG. 8. Hereinbelow, the controller of the synchronous motor is oneembodiment of the method for controlling a synchronous motor.

As shown in FIG. 8, in the current controller of the synchronous motoraccording to the embodiment, a power conversion circuit 84 is providedwith appropriate actual voltage commands Vuref, Vvref, and Vwref suchthat a synchronous motor 81 fed with power from the power conversioncircuit 84 approaches an actual command θref, and the controllercomprises: an actual position observation device 82 for providing anactual position θ of the synchronous motor 81; an actual currentobservation section 83 which observes a current of two phases or more ofthe synchronous motor 81 and provides actual currents Iu, Iv, and Iw; afirst coordinate conversion circuit 86 which converts, on the basis ofthe actual position θ, the actual currents Iu, Iv, and Iw into a d-axisactual current Id and a q-axis actual current Iq on the rotationalcoordinate axes which rotate synchronously with the rotor magnetic fluxvector of the synchronous motor; a machine control section 88 whichperforms machine control operation, to thereby provide a torque commandTref on the basis of the actual command θref, the actual position θ of arotor of the synchronous motor, and an estimated speed “w”; a currentcontrol section 87 which performs current control operation on the basisof the torque command Tref, the d-axis actual current Id, the q-axisactual current Iq, and the actual position θ, to thereby provide ad-axis voltage command Vdref and a q-axis voltage command Vqref; asecond coordinate conversion circuit 85 which provides the actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ, the d-axis voltage command Vdref, and the q-axis voltagecommand Vqref; and a first speed estimation section 89 for estimatingthe estimated speed “w” on the basis of the q-axis actual current Iq andthe q-axis voltage command Vqref.

The synchronous motor 81, the actual position observation device 82, theactual current observation section 83, the power conversion circuit 84,the second coordinate converter 85, the first coordinate conversioncircuit 86, the current control section 87, and the machine controlsection 88 are identical with related-art devices.

The first speed estimation section 89 produces the estimated speed “w”as follows:

Here, “s” designates a differential operator; Rq designates q-axisequivalent resistance; and Lq designates q-axis equivalent inductance.Lq1, Lq2 designate gains of the current observer which should be set ina pole assignment, where Iqob is a q-axis estimated current, and Vqob isa q-axis estimated voltage disturbance.Iqob*s=−Rq*Iqob/Lq+Lq 1*(Iq−Iqob)+(Vqob+Vqref)/Lq  (38)Vqob*s=Lq 2*(Iqfb−Iqob)  (39)w=−Vqob/φ  (40)

According to the current controller of the synchronous motor of theseventh embodiment, the first speed estimation section 89 estimates theestimated speed “w” in place of the differentiator 91 on the basis ofthe q-axis actual current Iq and the q-axis voltage command Vqref.Therefore, accuracy of the estimated speed “w” does not depend directlyon the resolution of the actual position θ.

Accordingly, even when the sampling time is shortened, superiorreadiness and superior robustness can be obtained without involvement ofan increase in the resolving power of an encoder.

An apparatus and method for controlling a synchronous motor according toan eight embodiment of the invention will be described by reference toFIG. 9. Hereinbelow, the controller of the synchronous motor is oneembodiment of the method for controlling a synchronous motor. As shownin FIG. 9, in the current controller of the synchronous motor accordingto the embodiment, the power conversion circuit 84 is provided withappropriate actual voltage commands Vuref, Vvref, and Vwref such thatthe synchronous motor 81 fed with power from the power conversioncircuit 84 approaches an actual command θref, and the controllercomprises: the actual position observation device 82 for providing anactual position θ of the synchronous motor 81; the actual currentobservation section 83 which observes a current of two phases or more ofthe synchronous motor 81 and provides actual currents Iu, Iv, and Iw;the first coordinate conversion circuit 86 which converts, on the basisof the actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Id and the q-axis actual current Iq on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; the machine controlsection 88 which performs machine control operation, to thereby providethe torque command Tref on the basis of the actual command θref, theactual position θ of the rotor of the synchronous motor, and theestimated speed “w”; the current control section 87 which performscurrent control operation on the basis of the torque command Tref, thed-axis actual current Id, the q-axis actual current Iq, and the actualposition θ, to thereby provide a d-axis voltage command Vdref and aq-axis voltage command Vqref; the second coordinate conversion circuit85 which provides the actual voltage commands Vuref, Vvref, and Vwref onthe basis of the actual position θ, the d-axis voltage command Vdref,and the q-axis voltage command Vqref; and a second speed estimationsection 90 for estimating the estimated speed “w” on the basis of thed-axis actual current Id, the q-axis actual current Iq, the d-axisvoltage command Vdref, and the q-axis voltage command Vqref.

The second speed estimation section 90 produces the estimated speed “w”as follows.

Here, Rd designates d-axis equivalent resistance; and Ld designatesd-axis equivalent inductance. Ld1, Ld2 designate gains of the currentobserver which should be set in a pole assignment, where Idob is ad-axis estimated current, and Vdob is a d-axis estimated voltagedisturbance.Idob*s=−Rd*Idob/Ld+Ld 1*(Id−Idob)−w*Iqob*Lq/Ld+(Vdref+Vdob)/Ld  (41)Vdob*s=Ld 2*(Id−Idob)  (42)Iqob*s=−Rq*Iqob/Lq+Lq 1*(Iq−Iqob)+w*Idob*Ld/Lq+(Vqob+Vqref)/Lq  (43)Vqob*s=Lq 2*(Iq−Iqob)  (44)w=−Vqob/φ  (45)

According to the current controller of the synchronous motor of theeighth embodiment, the second speed estimation section 90 estimates theestimated speed “w” in place of the differentiator 91, on the basis ofthe d-axis actual current Id, the q-axis actual current Iq, the d-axisvoltage command Vdref, and the q-axis voltage command Vqref. As aresult, the accuracy of the estimated speed “w” does not depend directlyon the resolution of the actual position θ. Accordingly, even when thesampling time is shortened, superior readiness and superior robustnesscan be obtained without involvement of an increase in the resolvingpower of an encoder. In addition, the second speed estimation section 90becomes superior to the first speed estimation section 89 in terms ofestimated accuracy of the estimated speed “w,” and hence a control gainof the machine control section can be set to a high level.

Although the invention has been described in detail by reference to aspecific embodiment, it is evident to a person skilled in the art thatthe invention is susceptible to various alterations and modificationswithout departing from the spirit and scope of the invention.

The present invention is based on Japanese Patent Application(JP-A-2001-203576) filed on Jul. 4^(th), 2001 and Japanese PatentApplication (JP-A-2001-209395) filed on Jul. 10^(th), 2001, and theircontents are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

According to a method for controlling an electric current of asynchronous motor defined in claim 1, a current feedback gain can be setto a high level by suppressing noise in a d-axis actual current Idfb andthat in a q-axis actual current Iqfb. Hence, even when variations arisein parameters or power of the synchronous motor 1 and the powerconversion circuit 4 under the influence of temperature, a superiorcurrent response characteristic can be obtained.

According to a method for controlling an electric current of asynchronous motor defined in claim 2, a current feedback gain can be setto a high level by suppressing noise in a d-axis actual current Idfb andthat in a q-axis actual current Iqfb. Hence, even when variations arisein parameters or power of the synchronous motor 1 and the powerconversion circuit 4 under the influence of temperature, a superiorcurrent response characteristic can be obtained. Further, when an abruptchange has arisen in the rotational speed of the synchronous motor, asuperior current response characteristic can be obtained by directlycompensating for an induced voltage.

According to a method for controlling an electric current of asynchronous motor defined in claim 3, a current feedback gain can be setto a high level by suppressing noise in the d-axis actual current Idfband that in the q-axis actual current Iqfb. Hence, even when variationsarise in parameters or power of the synchronous motor 1 and the powerconversion circuit 4 under the influence of temperature, a superiorcurrent response characteristic can be obtained. Further, when an abruptchange has arisen in the rotational speed of the synchronous motor, asuperior current response characteristic can be obtained by directlycompensating for an induced voltage. Moreover, a faster current responsecharacteristic in response to the command can be-obtained by directlycompensating for a d-axis second simulated voltage command Vdff and theq-axis second simulated voltage command Vqff.

According to a method for controlling an electric current of asynchronous motor defined in claim 4, a current feedback gain can be setto a high level by suppressing noise in the d-axis actual current Idfband that in the q-axis actual current Iqfb. Hence, even when variationsarise in parameters or power of the synchronous motor 1 and the powerconversion circuit 4 under the influence of temperature, a superiorcurrent response characteristic can be obtained. Further, when an abruptchange or fluctuation has arisen in a parameter of the synchronous motor1 and that of the power conversion circuit 4, a superior currentresponse characteristic can be obtained by directly compensating for ad-axis simulated disturbance voltage Vdob and a q-axis simulateddisturbance voltage Vqob.

According to a method for controlling an electric current of asynchronous motor defined in claim 5, a current feedback gain can be setto a high level by suppressing noise in the d-axis actual current Idfband that in the q-axis actual current Iqfb. Hence, even when variationsarise in parameters or power of the synchronous motor 1 and the powerconversion circuit 4 under the influence of temperature, a superiorcurrent response characteristic can be obtained. Further, when an abruptchange or fluctuation has arisen in a parameter of the synchronous motor1 and that-of the power conversion circuit 4, a superior currentresponse characteristic can be obtained by directly compensating for ad-axis simulated disturbance voltage Vdob and a q-axis simulateddisturbance voltage Vqob. Moreover, a faster current responsecharacteristic can be obtained by directly compensating for a d-axissecond simulated voltage command Vdff and a q-axis second simulatedvoltage command Vqff.

According to a method for controlling an electric current of asynchronous motor defined in claim 6, a current feedback gain can be setto a high level by suppressing noise in the d-axis actual current Idfband that in the q-axis actual current Iqfb. Hence, even when variationsarise in parameters or power of the synchronous motor 1 and the powerconversion circuit 4 under the influence of temperature, a superiorcurrent response characteristic can be obtained. Further, when an abruptchange or fluctuation has arisen in a parameter of the synchronous motor1 and that of the power conversion circuit 4, a superior currentresponse characteristic can be obtained by directly compensating for thed-axis simulated disturbance voltage Vdob and the q-axis simulateddisturbance voltage Vqob. Moreover, a faster current responsecharacteristic can be obtained by directly compensating for the d-axissecond simulated voltage command Vdff and the q-axis second simulatedvoltage command Vqff. In addition, even when an abrupt change has arisenin the rotational speed of the synchronous motor, a superior currentresponse characteristic can be obtained by directly compensating for theinduced voltage.

According to a current controller of a synchronous motor defined inclaim 7, feedback control is performed by use of a d-axis.simulatedcurrent Idob and a q-axis simulated current Iqob, both being obtained bya current observer section 10 a, in place of the measured currents Idfband Iqfb, thereby suppressing noise included in the measured currentsIdfb, Iqfb and enabling setting of the feedback gains kda and kqa tohigh levels. Hence, even when variations arise in parameters or power ofthe synchronous motor land the power conversion circuit 4 under theinfluence of temperature, a superior current response characteristic canbe obtained.

According to a current controller of a synchronous motor defined inclaim 8, feedback control is performed by use of the d-axis simulatedcurrent Idob and the q-axis simulated current Iqob, both being obtainedby the current observer section 10 b, in place of the measured currentsIdfb and Iqfb, thereby suppressing noise included in the measuredcurrents Idfb, Iqfb and enabling setting of the feedback gains kda andkqa to high levels. Hence, even when variations arise in parameters orpower of the synchronous motor 1 and the power conversion circuit 4under the influence of temperature, a superior current responsecharacteristic can be obtained. Further, when an abrupt change arises inthe rotational speed of the synchronous motor, estimation errors in thed-axis simulated current Idob and the q-axis simulated current Iqob,both being produced by the current observer section 10 b, are suppressedby compensating for the induced voltage on the basis of the inducedvoltage compensation section 7. Accordingly, even when an abrupt changearises in the rotational speed of the synchronous motor, a superiorcurrent response characteristic can be obtained.

According to a current controller of a synchronous motor defined inclaim 9, feedback control is performed by use of the d-axis simulatedcurrent Idob and the q-axis simulated current Iqob, both being obtainedby the current observer section 10 b, in place of the measured currentsIdfb and Iqfb, thereby suppressing noise included in the measuredcurrents Idfb, Iqfb and enabling setting of the feedback gains kda andkqa to high levels. Hence, even when variations arise in parameters orpower of the synchronous motor 1 and the power conversion circuit 4under the influence of temperature, a superior current responsecharacteristic can be obtained. Further, when an abrupt change arises inthe rotational speed of the synchronous motor, estimation errors in thed-axis simulated current Idob and the q-axis simulated current Iqob,both being produced by the current observer section 10 a, are suppressedby compensating for the induced voltage on the basis of the inducedvoltage compensation section 7. Accordingly, even when an abrupt changearises in the rotational speed of the synchronous motor, a superiorcurrent response characteristic can be obtained. Also, a faster currentresponse characteristic in response to the command can be obtained, byinputting the d-axis second simulated voltage command Vdff and theq-axis second simulated voltage command Vqff, both being produced by afeedforward control section 12, directly to a voltage commandsynthesizer 13.

According to a current controller of a synchronous motor defined inclaim 10, feedback control is performed by use of the d-axis simulatedcurrent Idob and the q-axis simulated current Iqob, both being producedby a current observer section 14 a, in place of the measured currentsIdfb and Iqfb, thereby suppressing noise included in the measuredcurrents Idfb, Iqfb and enabling setting of the feedback gains kda andkqa to high levels. Hence, even when variations arise in parameters orpower of the synchronous motor 1 and the power conversion circuit 4under the influence of temperature, a superior current responsecharacteristic can be obtained. A disturbance voltage component isdirectly compensated by inputting a d-axis simulated disturbance voltageVdob and a q-axis simulated disturbance voltage Vqob, both beingproduced by the current observer section 14 a, directly to the voltagecommand synthesizer 15. Accordingly, even when abrupt changes orfluctuations have arisen in a parameter of the synchronous motor 1 orthose of the power conversion circuit 4, a superior current responsecharacteristic can be obtained.

According to a current controller of a synchronous motor defined inclaim 11, feedback control is performed by use of the d-axis simulatedcurrent Idob and the q-axis simulated current Iqob, both being obtainedby a current observer section 14 a, in place of the measured currentsIdfb and Iqfb, thereby suppressing noise included in the measuredcurrents Idfb, Iqfb and enabling setting of the feedback gains kda andkqa to high levels. Hence, even when variations arise in parameters orpower of the synchronous motor 1 and the power conversion circuit 4under the influence of temperature, a superior current responsecharacteristic can be obtained. A disturbance voltage component isdirectly compensated by inputting the d-axis simulated disturbancevoltage Vdob and the q-axis simulated disturbance voltage Vqob, bothbeing produced by the current observer section 14 a, directly to thevoltage command synthesizer 15. Accordingly, even when abrupt changes orfluctuations have arisen in a parameter of the synchronous motor 1 orthose of the power conversion circuit 4, a superior current responsecharacteristic can be obtained. Also, a faster current responsecharacteristic in response to the command can be obtained, by inputtingthe d-axis second simulated voltage command Vdff and the q-axis secondsimulated voltage command Vqff, both being produced by a feedforwardcontrol section 12, directly to a voltage command synthesizer 16.

According to a current controller of a synchronous motor defined inclaim 12, feedback control is performed by use of the d-axis simulatedcurrent Idob and the q-axis simulated current Iqob, both being producedby a current observer section 14 b, in place of the measured currentsIdfb and Iqfb, thereby suppressing noise included in the measuredcurrents Idfb, Iqfb and enabling setting of the feedback gains kda andkqa to high levels. Hence, even when variations arise in parameters orpower of the synchronous motor land the power conversion circuit 4 underthe influence of temperature, a superior current response characteristiccan be obtained. A disturbance voltage component is directly compensatedby inputting the d-axis simulated disturbance voltage Vdob and theq-axis simulated disturbance voltage Vqob, both being produced by thecurrent observer section 14 b, directly to the voltage commandsynthesizer 15. Accordingly, even when abrupt changes or fluctuationshave arisen in a parameter of the synchronous motor 1 or those of thepower conversion circuit 4, a superior current response characteristiccan be obtained. Also, a faster current response characteristic inresponse to the command can be obtained, by inputting the d-axis secondsimulated voltage command Vdff and the q-axis second simulated voltagecommand Vqff, both being produced by a feedforward control section 12,directly to a voltage command synthesizer 16. Further, when an abruptchange arises in the rotational speed of the synchronous motor,estimation errors in the d-axis simulated current Idob and the q-axissimulated current Iqob, both being produced by the current observersection 14 b, are suppressed by compensating for the induced voltage onthe basis of the induced voltage compensation section 7. Accordingly,even when an abrupt change arises in the rotational speed of thesynchronous motor, a superior current response characteristic can beobtained.

According to a method for controlling a synchronous motor defined inclaim 13, a first speed estimation section estimates an estimated speed“w” on the basis of the q-axis actual current Iq and the q-axis voltagecommand Vqref. The accuracy of the estimated speed “w” does not dependdirectly on the resolution of the actual position θ. Accordingly, evenwhen the sampling time is shortened, superior readiness and superiorrobustness can be obtained without involvement of an increase in theresolving power of an encoder.

According to a method for controlling a synchronous motor defined inclaim 14, the estimated speed “w” is estimated on the basis of thed-axis actual current Id, the q-axis actual current Iq, the d-axisvoltage command Vdref, and the q-axis voltage command Vqref. As aresult, the accuracy of the estimated speed “w” does not depend directlyon the resolution of the actual position θ. Accordingly, even when thesampling time is shortened, superior readiness and superior robustnesscan be obtained without involvement of an increase in the resolvingpower of an encoder. In addition, the accuracy of the estimated speed“w” becomes higher by utilization of the d-axis actual current Id, theq-axis actual current Iq, the d-axis voltage command Vdref, and theq-axis voltage command Vqref. Hence, a control gain of the machinecontrol section can be set to a high level.

According to a controller of a synchronous motor defined in claim 15, afirst speed estimation section rather than a differentiator 91 estimatesan estimated speed “w” on the basis of the q-axis actual current Iq andthe q-axis voltage command Vqref. The accuracy of the estimated speed“w” does not depend directly on the resolution of the actual position θ.Accordingly, even when the sampling time is shortened, superiorreadiness and superior robustness can be obtained without involvement ofan increase in the resolving power of an encoder.

According to a controller of a synchronous motor defined in claim 16, asecond speed estimation section 90 rather than a differentiator 91estimates the estimated speed “w” on the basis of the d-axis actualcurrent Id, the q-axis actual current Iq, the d-axis voltage commandVdref, and the q-axis voltage command Vqref. As a result, the accuracyof the estimated speed “w” does not depend directly on the resolution ofthe actual position θ. Accordingly, even when the sampling time isshortened, superior readiness and superior robustness can be obtainedwithout involvement of an increase in the resolving power of an encoder.In addition, the second speed estimation section 90 becomes superior tothe first speed estimation section 89 in terms of estimation accuracy ofthe estimated speed “w.” Hence, a control gain of the machine controlsection can be set to a high level.

1. A method for controlling an electric current of a synchronous motorin which a power conversion circuit is provided with an appropriateactual voltage command such that an electric current flowing through thesynchronous motor fed with power from the power conversion circuitcoincides with a current command, the method comprising the steps of:converting electric currents Iu, Iv, and Iw, flowing through thesynchronous motor, into a d-axis actual current Idfb and a q-axis actualcurrent Iqfb on rotational coordinate axes which rotate synchronouslywith a rotor magnetic flux vector on the basis of an actual position θof the rotor of the synchronous motor; estimating a d-axis simulatedcurrent Idob and a q-axis simulated current Iqob on the basis of thed-axis actual current Idfb, the q-axis actual current Iqfb, a d-axisactual voltage command Vdref, and a q-axis voltage command Vqref;generating the d-axis actual voltage command Vdref and the q-axis actualvoltage command Vqref on the basis of a d-axis current command Idref, aq-axis current command Iqref, the d-axis simulated current Idob, and theq-axis simulated current Iqob; and converting the d-axis actual voltagecommand Vdref and the q-axis actual voltage command Vqref into actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ of a rotor of the synchronous motor.
 2. A method forcontrolling an electric current of a synchronous motor in which a powerconversion circuit is provided with an appropriate actual voltagecommand such that an electric current flowing through the synchronousmotor fed with power from the power conversion circuit coincides with acurrent command, the method comprising the steps of: converting electriccurrents Iu, Iv, and Iw flowing through the synchronous motor into ad-axis actual current Idfb and a q-axis actual current Iqfb onrotational coordinate axes which rotate synchronously with a rotormagnetic flux vector on the basis of an actual position θ of the rotorof the synchronous motor; estimating a d-axis simulated current Idob anda q-axis simulated current Iqob on the basis of the d-axis actualcurrent Idfb, the q-axis actual current Iqfb, a d-axis first simulatedvoltage command Vdo, and a q-axis first simulated voltage command Vqo;generating the d-axis third simulated voltage command Vdfb and theq-axis third simulated voltage command Vqfb on the basis of the d-axissecond simulated current command Idff, the q-axis second simulatedcurrent command Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; adding an induced voltage to the d-axis firstsimulated voltage command Vdo and the q-axis first simulated voltagecommand Vqo on the basis of the actual position θ of a rotor of thesynchronous motor, to thereby produce a d-axis actual voltage commandVdref and a q-axis actual voltage command Vqref; and converting thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref into actual voltage commands Vuref, Vvref, and Vwref onthe basis of the actual position θ of a rotor of the synchronous motor.3. A method for controlling an electric current of a synchronous motorin which a power conversion circuit is provided with an appropriateactual voltage command such that an electric current flowing through thesynchronous motor fed with power from the power conversion circuitcoincides with a current command, the method comprising the steps of:generating a d-axis second simulated current command Idff, a q-axissecond simulated current command Iqff, a d-axis second simulated voltagecommand Vdff, and a q-axis second simulated voltage command Vqff on thebasis of a d-axis current command Idref and a q-axis current commandIqref; converting electric currents Iu, Iv, and Iw flowing through thesynchronous motor into a d-axis actual current Idfb and a q-axis actualcurrent Iqfb on rotational coordinate axes which rotate synchronouslywith a rotor magnetic flux vector, on the basis of an actual position θof the rotor of the synchronous motor; estimating a d-axis simulatedcurrent Idob and a q-axis simulated current Iqob on the basis of thed-axis actual current Idfb, the q-axis actual current Iqfb, a d-axisfirst simulated voltage command Vdo, and a q-axis first simulatedvoltage command Vqo; generating a d-axis third simulated voltage commandVdfb and a q-axis third simulated voltage command Vqfb on the basis ofthe d-axis second simulated current command Idff, the q-axis secondsimulated current command Iqff, the d-axis simulated current Idob, andthe q-axis simulated current Iqob; generating the first d-axis firstsimulated voltage command Vdo and the q-axis first simulated voltagecommand Vqo on the basis of the d-axis third simulated voltage commandVdfb, the q-axis third simulated voltage command Vqfb, the d-axis secondsimulated voltage command Vdff, and the q-axis second simulated voltagecommand Vqff; adding an induced voltage to the d-axis first simulatedvoltage command Vdo and the q-axis first simulated voltage command Vqoon the basis of the actual position θ of a rotor of the synchronousmotor, to thereby produce a d-axis actual voltage command Vdref and aq-axis actual voltage command Vqref; and converting the d-axis actualvoltage command Vdref and the q-axis actual voltage command Vqref intoactual voltage commands Vuref, Vvref, and Vwref on the basis of theactual position θ of a rotor of the synchronous motor.
 4. A method forcontrolling an electric current of a synchronous motor in which a powerconversion circuit is provided with an appropriate actual voltagecommand such that an electric current flowing through the synchronousmotor fed with power from the power conversion circuit coincides with acurrent command, the method comprising the steps of: converting electriccurrents Iu, Iv, and Iw flowing through the synchronous motor into ad-axis actual current Idfb and a q-axis actual current Iqfb onrotational coordinate axes which rotate synchronously with a rotormagnetic flux vector, on the basis of an actual position θ of the rotorof the synchronous motor; estimating a d-axis simulated current Idob, aq-axis simulated current Iqob, a d-axis simulated disturbance voltageVdob, and a q-axis simulated voltage command Vqob on the basis of thed-axis actual current Idfb, the q-axis actual current Iqfb, a d-axisactual voltage command Vdref, and a q-axis actual voltage command Vqref;generating a d-axis first simulated voltage command Vdo and a q-axisfirst simulated voltage command Vqo on the basis of a d-axis currentcommand Idref, a q-axis current command Iqref, the d-axis simulatedcurrent Idob, and the q-axis simulated current Iqob; generating thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref on the basis of the d-axis third simulated voltage commandVdfb, the q-axis third simulated voltage command Vqfb, the d-axissimulated disturbance voltage Vdob, and the q-axis simulated disturbancevoltage Vqob; and converting the d-axis actual voltage command Vdref andthe q-axis actual voltage command Vqref into actual voltage commandsVuref, Vvref, and Vwref on the basis of the actual position θ of a rotorof the synchronous motor.
 5. A method for controlling an electriccurrent of a synchronous motor in which a power conversion circuit isprovided with an appropriate actual voltage command such that anelectric current flowing through the synchronous motor fed with powerfrom the power conversion circuit coincides with a current command, themethod comprising the steps of: generating a d-axis second simulatedcurrent command Idff, a q-axis second simulated current command Iqff, ad-axis second simulated voltage command Vdff, and a q-axis secondsimulated voltage command Vqff on the basis of a d-axis current commandIdref and a q-axis current command Iqref; converting electric currentsIu, Iv, and Iw flowing through the synchronous motor into a d-axisactual current Idfb and a q-axis actual current Iqfb on rotationalcoordinate axes which rotate synchronously with a rotor magnetic fluxvector, on the basis of an actual position θ of the rotor of thesynchronous motor; estimating a d-axis simulated current Idob, a q-axissimulated current Iqob, a d-axis simulated disturbance voltage Vdob, anda q-axis simulated disturbance voltage Vqob on the basis of the d-axisactual current Idfb, the q-axis actual current Iqfb, ad-axis actualvoltage command Vdref, and a q-axis actual voltage command Vqref;generating a d-axis third simulated voltage command Vdfb and a q-axisthird simulated voltage command Vqfb on the basis of the d-axis secondsimulated current command Idff, the q-axis second simulated currentcommand Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; generating the d-axis actual voltage commandVdref and the q-axis actual voltage command Vqref on the basis of thed-axis second simulated voltage command Vdff, the q-axis secondsimulated voltage command Vqff, the d-axis third simulated voltagecommand Vdfb, the q-axis third simulated voltage command Vqfb, thed-axis simulated disturbance voltage Vdob, and the q-axis simulateddisturbance voltage Vqob; and converting the d-axis voltage commandVdref and the q-axis actual voltage command Vqref into actual voltagecommands Vuref, Vvref, and Vwref on the basis of the actual position θof a rotor of the synchronous motor.
 6. A method for controlling anelectric current of a synchronous motor in which a power conversioncircuit with an appropriate actual voltage command such that an electriccurrent flowing through the synchronous motor fed with power from thepower conversion circuit coincides with a current command, the methodcomprising the steps of: generating a d-axis second simulated currentcommand Idff, a q-axis second simulated current command Iqff, a d-axissecond simulated voltage command Vdff, and a q-axis second simulatedvoltage command Vqff on the basis of a d-axis current command Idref anda q-axis current command Iqref; converting electric currents Iu, Iv, andIw flowing through the synchronous motor into a d-axis actual currentIdfb and a q-axis actual current Iqfb on rotational coordinate axeswhich rotate synchronously with a rotor magnetic flux vector, on thebasis of an actual position θ of the rotor of the synchronous motor;estimating a d-axis simulated current Idob, a q-axis simulated currentIqob, a d-axis simulated disturbance voltage Vdob, and a q-axissimulated disturbance voltage Vqob on the basis of the d-axis actualcurrent Idfb, the q-axis actual current Iqfb, a d-axis first simulatedvoltage command Vdo, and a q-axis actual voltage command Vqo; generatinga d-axis third simulated voltage command Vdfb and a q-axis thirdsimulated voltage command Vqfb on the basis of the d-axis secondsimulated current command Idff, the q-axis second simulated currentcommand Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; generating the d-axis first simulated voltagecommand Vdo and the q-axis actual voltage command Vqo on the basis ofthe d-axis second simulated voltage command Vdff, the q-axis secondsimulated voltage command Vqff, the d-axis third simulated voltagecommand Vdfb, the q-axis third simulated voltage command Vqfb, thed-axis simulated disturbance voltage Vdob, and the q-axis simulateddisturbance voltage Vqob; adding an induced voltage to the d-axis firstsimulated voltage command Vdo and the d-axis first simulated voltagecommand Vqo on the basis of an actual position θ, to thereby produce ad-axis actual voltage command Vdref and a q-axis actual voltage commandVqref; and converting the d-axis voltage command Vdref and the q-axisactual voltage command Vqref into actual voltage commands Vuref, Vvref,and Vwref on the basis of the actual position θ of a rotor of thesynchronous motor.
 7. A current controller of a synchronous motor inwhich a power conversion circuit 4 is provided with actual voltagecommands Vuref, Vvref, and Vwref such that a d-axis actual current Idfband a q-axis actual current Iqfb on rotational coordinate axes whichrotate synchronously with a rotor magnetic flux vector of a synchronousmotor 1 coincide with a d-axis current command Idref and a q-axiscurrent command Iqref, the controller comprising the steps of: an actualposition observation device 2 for providing an actual position θ of thesynchronous motor; an actual current observation section 3 whichobserves a current of two phases or more of the synchronous motor andprovides actual currents Iu, Iv, and Iw; a second coordinate converter 6which converts, on the basis of the actual position θ, the actualcurrents Iu, Iv, and Iw into the d-axis actual current Idfb and theq-axis actual current Iqfb on the rotational coordinate axes whichrotate synchronously with the rotor magnetic flux vector of thesynchronous motor; a current observer 10 a which estimates a d-axissimulated current Idob and a q-axis simulated current Iqob on the basisof the d-axis actual current Idfb, the q-axis actual current Iqfb, ad-axis actual voltage command Vdref, and a q-axis actual voltage commandVqref; a feedback control section 9 a which produces the d-axis actualvoltage command Vdref and the q-axis actual voltage command Vqref on thebasis of the d-axis current command Idref, the q-axis current commandIqref, the d-axis simulated current Idob, and the q-axis simulatedcurrent Iqob; and a first coordinate converter 5 for converting thed-axis actual voltage command Vdref and the q-axis actual voltagecommand Vqref into the actual voltage commands Vuref, Vvref, and Vwrefon the basis of an actual position θ of a rotor of the synchronousmotor.
 8. A current controller of a synchronous motor in which a powerconversion circuit 4 is provided with actual voltage commands Vuref,Vvref, and Vwref such that a d-axis actual current Idfb and a q-axisactual current Iqfb on rotational coordinate axes which rotatesynchronously with the rotor magnetic flux vector of a synchronous motor1 coincide with a d-axis current command Idref and a q-axis currentcommand Iqref, the controller comprising the steps of: an actualposition observation device 2 for providing an actual position θ of thesynchronous motor; an actual current observation section 3 whichobserves a current of two phases or more of the synchronous motor andprovides actual currents Iu, Iv, and Iw; a second coordinate converter 6which converts, on the basis of the actual position θ, the actualcurrents Iu, Iv, and Iw into the d-axis actual current Idfb and theq-axis actual current Iqfb on the rotational coordinate axes whichrotate synchronously with the rotor magnetic flux vector of thesynchronous motor; a current observer 10 b which estimates a d-axissimulated current Idob and a q-axis simulated current Iqob on the basisof the d-axis actual current Idfb, the q-axis actual current Iqfb, ad-axis first simulated voltage command Vdo, and a q-axis first simulatedvoltage command Vqo; a feedback control section 9 b which produces thed-axis first simulated voltage command Vdo and the q-axis firstsimulated voltage command Vqo on the basis of the d-axis current commandIdref, the q-axis current command Iqref, the d-axis simulated currentIdob, and the q-axis simulated current Iqob; a speed generator 8 forproducing an actual speed “w” on the basis of the actual position θ; aninduced voltage compensation section 7 which adds an induced voltage tothe d-axis first simulated voltage command Vdo and the q-axis firstsimulated voltage command Vqo on the basis of the d-axis first simulatedvoltage command Vdo, the q-axis first simulated voltage command Vqo, andthe actual speed “w,” to thereby produce the d-axis actual voltagecommand Vdref and the q-axis actual voltage command Vqref; and a firstcoordinate converter 5 for converting the d-axis actual voltage commandVdref and the q-axis actual voltage command Vqref into the actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ.
 9. A current controller of a synchronous motor in which apower conversion circuit 4 is provided with actual voltage commandsVuref, Vvref, and Vwref such that a d-axis actual current Idfb and aq-axis actual current Iqfb on rotational coordinate axes which rotatesynchronously with a rotor magnetic flux vector of a synchronous motor 1coincide with a d-axis current command Idref and a q-axis currentcommand Iqref, the controller comprising the steps of: an actualposition observation device 2 for providing an actual position θ of thesynchronous motor; an actual current observation section 3 whichobserves a current of two phases or more of the synchronous motor andprovides actual currents Iu, Iv, and Iw; a second coordinate converter 6which converts, on the basis of the actual position θ, the actualcurrents Iu, Iv, and Iw into the d-axis actual current Idfb and theq-axis actual current Iqfb on the rotational coordinate axes whichrotate synchronously with the rotor magnetic flux vector of thesynchronous motor; a current observer 10 b which estimates a d-axissimulated current Idob and a q-axis simulated current Iqob on the basisof the d-axis actual current Idfb, the q-axis actual current Iqfb,ad-axis first simulated voltage command Vdo, and a q-axis firstsimulated voltage command Vqo; a feedforward control section 12 whichproduces a d-axis second simulated current command Idff, a q-axis secondsimulated current command Iqff, a d-axis second simulated voltagecommand Vdff, and a q-axis second simulated voltage command Vqff on thebasis of the d-axis current command Idref and the q-axis current commandIqref; a feedback control section 11 which produces a d-axis thirdsimulated voltage command Vdfb and a q-axis third simulated voltagecommand Vqfb on the basis of the d-axis second simulated current commandIdff, the q-axis second simulated current command Iqff, the d-axissimulated current Idob, and the q-axis simulated current Iqob; a voltagecommand synthesizer 13 which produces the d-axis first simulated voltagecommand Vdo and the q-axis first simulated voltage command Vqo on thebasis of the d-axis third simulated voltage command Vdfb, the q-axisthird simulated voltage command Vqfb, the d-axis second simulatedvoltage command Vdff, and the q-axis second simulated voltage commandVqff; a current feedback control section 9 b which produces the d-axisfirst simulated voltage command Vdo and the q-axis first simulatedvoltage command Vqo on the basis of the d-axis current command Idref,the q-axis current command Iqref, the d-axis simulated current Idob, andthe q-axis simulated current Iqob; a speed generator 8 for producing anactual speed “w” on the basis of the actual position θ; an inducedvoltage compensation section 7 which adds an induced voltage to thed-axis first simulated voltage command Vdo and the q-axis firstsimulated voltage command Vqo on the basis of the d-axis first simulatedvoltage command Vdo, the q-axis first simulated voltage command Vqo, andthe actual speed “w,” to thereby produce the d-axis actual voltagecommand Vdref and the q-axis actual voltage command Vqref; and a firstcoordinate converter 5 for converting the d-axis actual voltage commandVdref and the q-axis actual voltage command Vqref into the actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ.
 10. A current controller of a synchronous motor in which apower conversion circuit 4 is provided with actual voltage commandsVuref, Vvref, and Vwref such that a d-axis actual current Idfb and aq-axis actual current Iqfb on rotational coordinate axes which rotatesynchronously with the rotor magnetic flux vector of a synchronous motor1 coincide with a d-axis current command Idref and a q-axis currentcommand Iqref, the controller comprising the steps of: an actualposition observation device 2 for providing an actual position θ of thesynchronous motor; an actual current observation section 3 whichobserves a current of two phases or more of the synchronous motor andprovides actual currents Iu, Iv, and Iw; a second coordinate converter 6which converts, on the basis of the actual position θ, the actualcurrents Iu, Iv, and Iw into the d-axis actual current Idfb and theq-axis actual current Iqfb on the rotational coordinate axes whichrotate synchronously with the rotor magnetic flux vector of thesynchronous motor; a current observer 14 a which estimates a d-axissimulated current Idob, a q-axis simulated current Iqob, a d-axissimulated disturbance voltage Vdob, and a q-axis simulated disturbancevoltage Vqob on the basis of the d-axis actual current Idfb, the q-axisactual current Iqfb, the d-axis actual voltage command Vdref, and theq-axis actual voltage command Vqref; a feedback control section 9 bwhich produces a d-axis first simulated voltage command Vdo and a q-axisfirst simulated voltage command Vqo on the basis of the d-axis currentcommand Idref, the q-axis current command Iqref, the d-axis simulatedcurrent Idob, and the q-axis simulated current Iqob; a voltage commandsynthesizer 15 which produces the d-axis actual voltage command Vdrefand the q-axis actual voltage command Vqref on the basis of the d-axisthird simulated voltage command Vdfb, the q-axis third simulated voltagecommand Vqfb, the d-axis simulated disturbance voltage Vdob, and theq-axis simulated disturbance voltage Vqob; and a first coordinateconverter 5 for converting the d-axis actual voltage command Vdref andthe q-axis actual voltage command Vqref into the actual voltage commandsVuref, Vvref, and Vwref on the basis of the actual position θ.
 11. Acurrent controller of a synchronous motor which provides a powerconversion circuit 4 with actual voltage commands Vuref, Vvref, andVwref such that a d-axis actual current Idfb and a q-axis actual currentIqfb on rotational coordinate axes which rotate synchronously with therotor magnetic flux vector of a synchronous motor 1 coincide with ad-axis current command Idref and a q-axis current command Iqref, thecontroller comprising the steps of: an actual position observationdevice 2 for providing an actual position θ of the synchronous motor; anactual current observation section 3 which observes a current of twophases or more of the synchronous motor and provides actual currents Iu,Iv, and Iw; a second coordinate converter 6 which converts, on the basisof the actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb onrotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; a feedforward controlsection 12 which produces a d-axis second simulated current commandIdff, a q-axis second simulated current command Iqff, a d-axis secondsimulated voltage command Vdff, and a q-axis second simulated voltagecommand Vqff on the basis of the d-axis current command Idref and theq-axis current command Iqref; a current observer 14 a which estimates ad-axis simulated disturbance current Idob and a q-axis simulateddisturbance current Iqob on the basis of the d-axis actual current Idfb,the q-axis actual current Iqfb, the q-axis actual voltage command Vdref,and the q-axis actual voltage command Vqref; a feedback control section11 which produces a d-axis third simulated voltage command Vdfb and aq-axis third simulated voltage command Vqfb on the basis of the d-axissecond simulated current command Idff, the q-axis second simulatedcurrent command Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; a voltage command synthesizer 16 which producesa d-axis actual voltage command Vdref and a q-axis actual voltagecommand Vqref on the basis of the d-axis second simulated voltagecommand Vdff, the q-axis second simulated voltage command Vqff, thed-axis third simulated voltage command Vdfb, the q-axis third simulatedvoltage command Vqfb, the d-axis simulated disturbance voltage Vdob, andthe q-axis simulated disturbance voltage Vqob; and a first coordinateconverter 5 for converting the d-axis actual voltage command Vdref andthe q-axis actual voltage command Vqref into the actual voltage commandsVuref, Vvref, and Vwref on the basis of the actual position θ.
 12. Acurrent controller of a synchronous motor in which a power conversioncircuit 4 is provided with actual voltage commands Vuref, Vvref, andVwref such that a d-axis actual current Idfb and a q-axis actual currentIqfb on rotational coordinate axes which rotate synchronously with arotor magnetic flux vector of a synchronous motor 1 coincide with ad-axis current command Idref and a q-axis current command Iqref, thecontroller comprising the steps of: an actual position observationdevice 2 for providing an actual position θ of the synchronous motor; anactual current observation section 3 which observes a current of twophases or more of the synchronous motor and provides actual currents Iu,Iv, and Iw; a second coordinate converter 6 which converts, on the basisof the actual position θ, the actual currents Iu, Iv, and Iw into thed-axis actual current Idfb and the q-axis actual current Iqfb on therotational coordinate axes which rotate synchronously with the rotormagnetic flux vector of the synchronous motor; a feedforward controlsection 12 which produces a d-axis second simulated current commandIdff, a q-axis second simulated current command Iqff, a d-axis secondsimulated voltage command Vdff, and a q-axis second simulated voltagecommand Vqff on the basis of the d-axis current command Idref and theq-axis current command Iqref; a current observer 14 b which estimates ad-axis simulated current Idob, a q-axis simulated current Iqob, a d-axissimulated disturbance voltage Vdob, and a q-axis simulated disturbancevoltage Vqob on the basis of the d-axis actual current Idfb, the q-axisactual current Iqfb, a d-axis first simulated voltage command Vdo, and aq-axis actual voltage command Vqo; a feedback control section 11 whichproduces a d-axis third simulated voltage command Vdfb and a q-axisthird simulated voltage command Vqfb on the basis of the d-axis secondsimulated current command Idff, the q-axis second simulated currentcommand Iqff, the d-axis simulated current Idob, and the q-axissimulated current Iqob; a voltage command synthesizer 17 which producesthe d-axis first simulated voltage command Vdo and the q-axis actualvoltage command Vqo on the basis of the d-axis second simulated voltagecommand Vdff, the q-axis second simulated voltage command Vqff, thed-axis third simulated voltage command Vdfb, and the q-axis thirdsimulated voltage command Vqfb; a speed generator 8 for producing anactual speed “w” on the basis of the actual position θ; an inducedvoltage compensation section 7 which adds an induced voltage to thed-axis first simulated voltage command Vdo and the q-axis firstsimulated voltage command Vqo on the basis of the d-axis first simulatedvoltage command Vdo, the q-axis first simulated voltage command Vqo, andthe actual speed “w,” to thereby produce the d-axis actual voltagecommand Vdref and the q-axis actual voltage command Vqref; and a firstcoordinate converter 5 for converting the d-axis actual voltage commandVdref and the q-axis actual voltage command Vqref into the actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ.
 13. A method for controlling a synchronous motor in which apower conversion circuit is provided with appropriate actual voltagecommands Vuref, Vvref, and Vwref such that a synchronous motor fed withpower from the power conversion circuit approaches an actual commandθref, the method comprising the steps of: performing a machine controloperation on the basis of an actual command θref, an actual position θof a rotor of the synchronous motor, and an estimated speed “w,” tothereby provide a torque command Tref; converting electric currents Iu,Iv, and Iw flowing through the synchronous motor into a d-axis actualcurrent Id and a q-axis actual current Iq on rotational coordinate axeswhich rotate synchronously with a rotor magnetic flux vector, on thebasis of an actual position θ of the rotor of the synchronous motor;performing a current control operation on the basis of the actualposition θ, the torque command Tref, the d-axis actual current Id, andthe q-axis actual current Iq, to thereby provide a d-axis voltagecommand Vdref and a q-axis voltage command Vqref; converting the d-axisvoltage command Vdref and the q-axis voltage command Vqref into actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ; and estimating an estimated speed “w” on the basis of theq-axis actual current Iq and the q-axis voltage command Vqref.
 14. Amethod for controlling a synchronous motor in which a power conversioncircuit is provided with appropriate actual voltage commands Vuref,Vvref, and Vwref such that a synchronous motor fed with power from thepower conversion circuit approaches an actual command θref, the methodcomprising the steps of: performing a machine control operation on thebasis of the actual command θref, an actual position θ of a rotor of thesynchronous motor, and an estimated speed “w,” to thereby provide atorque command Tref; converting electric currents Iu, Iv, and Iw flowingthrough the synchronous motor into a d-axis actual current Id and aq-axis actual current Iq on rotational coordinate axes which rotatesynchronously with a rotor magnetic flux vector on the basis of anactual position θ of the rotor of the synchronous motor; performance ofcurrent control operation on the basis of the actual position θ, thetorque command Tref, the d-axis actual current Id, and the q-axis actualcurrent Iq, to thereby provide a d-axis voltage command Vdref and aq-axis voltage command Vqref; converting the d-axis voltage commandVdref and the q-axis voltage command Vqref into actual voltage commandsVuref, Vvref, and Vwref on the basis of the actual position θ; andestimating an estimated speed “w” on the basis of the d-axis actualcurrent Id, the q-axis actual current Iq, the d-axis voltage commandVdref, and the q-axis voltage command Vqref.
 15. A controller of asynchronous motor in which a power conversion circuit 84 is providedwith appropriate actual voltage commands Vuref, Vvref, and Vwref suchthat a synchronous motor 81 fed with power from the power conversioncircuit 84 approaches an actual command θref, the controller comprisingthe steps of: an actual position observation device 82 for providing anactual position θ of the synchronous motor 81; an actual currentobservation section 83 which observes a current of two phases or more ofthe synchronous motor 81 and provides actual currents Iu, Iv, and Iw; afirst coordinate conversion circuit 86 which converts, on the basis ofthe actual position θ, the actual currents Iu, Iv, and Iw into a d-axisactual current Id and a q-axis actual current Iq on the rotationalcoordinate axes which rotate synchronously with the rotor magnetic fluxvector of the synchronous motor; a machine control section 88 whichperforms machine control operation, to thereby provide a torque commandTref on the basis of the actual command θref, the actual position θ of arotor of the synchronous motor, and the estimated speed “w”; a currentcontrol section 87 which performs current control operation on the basisof the torque command Tref, the d-axis actual current Id, the q-axisactual current Iq, and the actual position θ, to thereby provide ad-axis voltage command Vdref and a q-axis voltage command Vqref; asecond coordinate conversion circuit 85 which provides the actualvoltage commands Vuref, Vvref, and Vwref on the basis of the actualposition θ, the d-axis actual voltage command Vdref, and the q-axisvoltage command Vqref; and a first speed estimation section 89 forestimating the estimated speed “w” on the basis of the q-axis actualcurrent Iq and the q-axis voltage command Vqref.
 16. A controller of asynchronous motor in which a power conversion circuit 84 is providedwith appropriate actual voltage commands Vuref, Vvref, and Vwref suchthat a synchronous motor 81 fed with power from the power conversioncircuit 84 approaches an actual command θref, the controller comprisingthe steps of: an actual position observation device 82 for providing anactual position θ of the synchronous motor 81; an actual currentobservation section 83 which observes a current of two phases or more ofthe synchronous motor 81 and provides actual currents Iu, Iv, and Iw; afirst coordinate conversion circuit 86 which converts, on the basis ofthe actual position θ, the actual currents Iu, Iv, and Iw into a d-axisactual current Id and a q-axis actual current Iq on the rotationalcoordinate axes which rotate synchronously with the rotor magnetic fluxvector of the synchronous motor; a machine control section 88 whichperforms machine control operation, to thereby provide the torquecommand Tref on the basis of the actual command θref, the actualposition θ of the rotor of the synchronous motor, and an estimated speed“w”; a current control section 87 which performs current controloperation on the basis of the torque command Tref, the d-axis actualcurrent Id, the q-axis actual current Iq, and the actual position θ, tothereby provide a d-axis voltage command Vdref and a q-axis voltagecommand Vqref; a second coordinate conversion circuit 85 which providesthe actual voltage commands Vuref, Vvref, and Vwref on the basis of theactual position θ, the d-axis actual voltage command Vdref, and theq-axis voltage command Vqref; and a second speed estimation section 90for estimating the estimated speed “w” on the basis of the d-axis actualcurrent Id, the q-axis actual current Iq, the d-axis voltage commandVdref, and the q-axis voltage command Vqref.